Contribution Of Individual Factors Research Articles

의과대학생의 다문화사회에 대한 태도

This study was aimed at identifying the types of attitude of multicultural society among medical student. Q-methodology focusing on individual subjectivity was used with data collected in November 2019. Forty-two Q-statements were selected and scored by the 20 participants on a 9-point scale with normal distribution. The data were analyzed using the PC-QUANL program. A total of 20 medical students were classified into 2 factors based on the following viewpoints: concern-acceptance (type 1), boundary-adaptation (type 2). The 2 factors accounted for 49.22% of the total variance. Individual contributions of factors 1 and 2 were 28.25% and 20.97%, respectively. The major contribution of this study is the clarification of medical students’ subjective perceptions of multicultural society. These findings can be used in formulating effective strategies for multicultural society and comprehending enhancement program on multicultural society from medical students’ education or organization program is needed concerning doctors provide effective health and care without bias.

Spatial prediction of soil nutrients from soil, topography and environmental attributes in the northern part of Ekiti State, Nigeria

Knowledge of soil nutrient's spatial distribution and variability is useful for determining the balanced use of fertilizer inputs and for decisions making on the acquisition of land for any activity that will have its base on the lithosphere portion of the earth. This study presents statistical model for the prediction of top soil nutrients (Soil Organic Matter (SOM), Potassium (K), Phosphorus (P) and Nitrogen (N)) from soil and topographic attributes in Ekiti north, Ekiti state, Nigeria using geospatial techniques. Three topographic attributes (elevation, slope and curvature), one environmental variable (Land surface temperature, LST), one vegetation attribute (Normalized difference vegetation index (NDVI)) and four soil attributes (Water holding capacity, and bulk density) were employed to predict the spatial distribution of soil nutrient (N, P, K, SOM) in the study area. 66 samples of top soil nutrient of were collected within the study area. Topographic attributes were extracted from the obtained Digital Elevation Model (DEM) and Land use data while the soil attributes were derived from existing methodology by soil characteristics and Land use data. The derived attributes were statistically correlated with the sampled soil nutrients (N, P, K, SOM) to establish their relationships. Using Multiple Linear Regression Analysis, the contributions of individual factors in the prediction of soil nutrient (N, P, K, SOM) were established and soil nutrient model developed. The model was used to spatially predict the distribution of top soil nutrient in the study area. Results show both negative and positives correlation between the attributes and the soil nutrient (N, P, K, SOM). Spatially, the predicted top soil nutrient compared considerably well with the observed top soil nutrients.

Evaluation of Changes in Expected Ultimate Recovery for US Gulf of Mexico Oil and Gas Fields, 1975–2016

Quantifying the change in field expected ultimate recovery across time is an old and complex topic fraught with ambiguity and misinterpretation. In this paper, changes in recovery estimates performed by the Bureau of Ocean Energy Management in the US Gulf of Mexico are evaluated based on 782 offshore fields that began producing after 1975 and ceased production before 2017. At the time of first production, field expected ultimate recovery estimates totaled 6.3 billion barrels oil equivalent (38.6 exajoules), but by the end of their life, the fields produced 8.5 billion barrels oil equivalent (52 exajoules), a 35% growth. On an individual field basis, however, median recovery estimates grew less than 2%. The purpose of this paper is to explain the differences in these two statistics and quantify how expected ultimate recovery is influenced by field age, discovery year, reserve category, peak ratio, product type, size, and water depth to understand better the contribution of individual factors in reserves evaluation. Consistent interpretation of reserves category is probably the most important factor in application. Field age and size are positively correlated with changes in expected ultimate recovery in both the shallow water and deepwater regions of the US Gulf of Mexico, pre- and post-1988 evaluation periods are a significant factor, and a development variable referred to as peak ratio exhibits a meaningful correspondence. The results of this analysis show that Bureau of Ocean Energy Management procedures for expected ultimate recovery estimation in the US Gulf of Mexico post-1988 are consistent with the application of probable reserves classifications; these highlight the need for a precise understanding of factor inputs in reserves growth studies.

Exploring Probabilistic Network-Based Modeling of Multidimensional Factors Associated with Country Risk.

Assessment of country risk provides a vital source of information to organizations for expanding and globalizing their operations. Various rating agencies are involved in developing models for assessing country risk, which utilize different statistical techniques for establishing the overall impact of individual factors on country risk. The main limitation of existing studies on country risk is their limited focus on exploring the relative contribution of individual factors to country risk in a probabilistic network setting. Utilizing real data, we develop a probabilistic network model that captures dependencies among multidimensional factors associated with country risk. Further, we assess the network-wide vulnerability and resilience potential of individual factors to identify critical factors. The findings of this study provide policy-makers with some unique insights into prioritizing strategies to mitigate country risk. Further, this study provides the context for multinational enterprises to utilize the proposed methodology for prioritizing key factors associated with the relative variables of interest such as regional stability and business environment among others.

Code-Switching in Linguistics: A Position Paper

This paper provides a critical review of the state of the art in code-switching research being conducted in linguistics. Three issues of theoretical and practical importance are explored: (a) code-switching vs. borrowing; (b) grammaticality; and (c) variability vs. uniformity, and I take a position on all three issues. Regarding switching vs. borrowing, I argue that not all lone other-language items are borrowings once more subtle measures of integration are used. I defend the use of empirical data to compare competing theoretical frameworks of grammaticality, and I exemplify quantitative research on variability in code-switching, showing that it also reveals uniformity and the possible influence of community norms. I conclude that more research is needed on a range of bilingual communities in order to determine the relative contribution of individual factors, processing and community norms to the variability and uniformity of code-switching.

Современные особенности трансформации мирового и российского рынков труда

The article is devoted to the assessment of the impact of modern digital technologies on the world and Russian labor market. The relevance of the chosen problem is explained by the fact that the achieved level of digital development of society has a signifi cant impact on the size of labor markets, the qualifi cation composition of workers, the demand for certain professions. The article presents the results of the analysis of the impact of digital technology on the growth of Russia’s GDP, the contribution of individual factors of growth in value added of diff erent sectors of the economy, including the sectoral dimension, the dynamics
 of digital technologies across regions of the country. The article presents the results of studies characterizing new trends in the labor market, formed as a response to the increasingly active penetration of the digital economy in the socioeconomic sphere of society.

Hubungan Faktor Individu dan Lingkungan dengan Perilaku Menyalahgunakan Napza di Lembaga Pemasyarakatan Kelas II.a Pekanbaru

In 2015 the NAPZA case in Riau expected to increase sharply compared to 2014 due to its geographical location that surrounded by the ocean that it had a beach which was easy for a place for drug traffic. Individual factors that cause drug abuse were curiosity, desires to be accepted by the group, following tendencies, seeking pleasure, seeking attention and imitating famous people. Whereas environmental factors were from family relations who were not harmonious, poor interpersonal relationships, parents/family members were also drug users, the communities are less concerned, lack social control and group pressure. The purpose of this study is to identify the relationship between individual factors and the environment with drug abuse in class II A prisons in Pekanbaru. This research was conducted from March to August 2015 with a cross-sectional analytic design on 89 assisted residents. The results showed that all individual and environmental factors had a relationship with drug abuse behaviour except for the environmental sub-variables, namely parents/family members as well as users. The contribution of Individual factors in drug abuse indicated that of the six most prominent individual factors are the average curiosity of the inmates is 75.78 ± 15.987 (the lowest results are 25, and the highest is 100. The least was the common desire to seek attention in abusing NAPZA is 52.83 ± 18.018 (the lowest results are 8, and the highest is 100. The results of this study could use as material for coaching activities related to individual and environmental factors in prison.

Sensitivity analysis as a tool to optimise Human Development Index

Research background: Composite indicators are commonly used as an approximation tool to measure economic development, the standard of living, competitiveness, fairness, effectiveness, and many others being willingly implemented into many different research disciplines. However, it seems that in most cases, the variable weighting procedure is avoided or erroneous since, in most cases, the so-called ?weights by belief? are applied. As research show, it can be frequently observed that weights do not equal importance in composite indicators. As a result, biased rankings or grouping of objects are obtained.
 Purpose of the article: The primary purpose of this article is to optimise and improve the Human Development Index, which is the most commonly used composite indicator to rank countries in terms of their socio-economic development. The optimisation will be done by re-scaling the current weights, so they will express the real impact of every single component taken into consideration during HDI?s calculation process.
 Methods: In order to achieve the purpose mentioned above, the sensitivity analysis tools (mainly the first-order sensitivity index) were used to determine the appropriate weights in the Human Development Index. In the HDI?s resilience evaluation process, the Monte Carlo simulations and full-Bayesian Gaussian processes were applied. Based on the adjusted weights, a new ranking of countries was established and compiled with the initial ranking using, among others, Kendall tau correlation coefficient.
 Findings & Value added: Based on the data published by UNDP for 2017, it has been shown that the Human Development Index is built incorrectly by putting equal weights for all of its components. The weights proposed by the sensitivity analysis better reflect the actual contribution of individual factors to HDI variability. Re-scaled Human Development Index constructed based on proposed weights allow for better differentiation of countries due to their socio-economic development.

Obesity and nonalcoholic fatty liver disease associated with adenocarcinoma in patients with lung cancer.

Lung cancer has become the leading cause of cancer-related deaths around the world. In addition to genetic risk factors and smoking, the metabolic risk factors remain to be elusive.To evaluate the associations between obesity, nonalcoholic fatty liver disease (NAFLD) and pulmonary adenocarcinoma in patients with lung cancer.Consecutive operation-proven lung cancer patients with assessment of metabolic disorders and liver ultrasound in 2009 and 2013 were retrospectively enrolled. T-test and multivariate logistic regression were applied to evaluate the contribution of individual factors to lung adenocarcinoma, as well as the synergistic effects between these factors.Among 3664 lung cancer patients with ultrasound examination, 2844 cases were enrolled for further analysis. Of them, 1053 (37.0%) were females, 1242 (43.7%) were cigarette smokers, 1658 (58.3%) were diagnosed as lung adenocarcinoma, 744 (26.2%) had obesity, and 614 (21.6%) had NAFLD. Proportion of female gender, nonsmoker, obesity, NAFLD, and serum lipid levels in patients with adenocarcinoma were significantly higher than those in other subtypes of lung cancer, and in 2013 than in 2009 (all P < .01). NAFLD and obesity were shown as independent factors and positively associated with pulmonary adenocarcinoma, along with female gender and nonsmoking, higher serum levels of cholesterol. NAFLD and other contributing factors exhibited no synergistic effects on adenocarcinoma.Obesity and NAFLD might increase the risk for pulmonary adenocarcinoma, especially in nonsmoking females, and underscore the need for further study into carcinogenic mechanisms and preventive interventions.

Methodical approach to the assessment of financial security of the region in the context of decentralization

The purpose of the research is to improve the methodological approach to assessing the financial security of the region in the context of decentralization, which, unlike the existing ones, makes it possible to determine the ways of ensuring the financial security of the regions through an integrated assessment of the contribution of individual factors and types of regulation to the final state of the financial security of the territories. Methodology. The methodological approach to the assessment of the financial security of the region under decentralization has been improved based on the application of normalization of the system of indicators and construction of integral indices by the type of impact indicator (exogenous or endogenous) and factors: decentralization, socio-economic status and fiscal policy of the regions. Individual time series have been identified and evaluated for each of these integrated indicators. Results. Based on the research, the methodological approach to the assessment of the financial security of the region under decentralization conditions has been improved, which makes it possible to determine the ways of ensuring the financial security of the regions by assessing the contribution of individual factors and types of regulation to the financial security. These individual contributions are grouped together to reflect the type of impact indicator (exogenous or endogenous) and factors such as decentralization, socio-economic status and fiscal policies of the regions. The categories of integrated indicators proposed in the article are useful for monitoring financial security drivers, making it clear what affects the financial security of a country under decentralization, how systemic events in the process of decentralization affect the financial security of regions over time. Practical meaning. The research identified three groups of regions of Ukraine in terms of their financial security: financially secure regions, which during the entire observation period were ascertained: a high integral financial security index (Dnipropetrovsk, Kyiv regions) and a sufficient integral financial security index (Lviv, Zaporizhzhya, Odesa, Poltava and Kharkiv regions); financially unstable regions where there is a potential for strengthening financial security (Vinnytsia, Donetsk, Kirovohrad, Mykolaiv, Cherkasy regions), but there is also a likelihood of aggravation of a negative financial situation (Ivano-Frankivsk, Zhytomyr, Sumy, Kherson, Khmelnytsky, Chernihiv regions); financially dangerous regions, which are dependent on state support, are not able to independently fulfill the majority of delegated to the local level of authority and to finance the economic development of the region (Volyn, Luhansk, Transcarpathian, Rivne, Ternopil, Chernivtsi regions). Therefore, the advantage of using this system of integrated indicators is that they give the developers of national regional policy and internal regional policy an up-to-date picture of the financial security situation in the region, wider than that provided only by some unsystematic indicators. Prospects for further research. The prospect for further research should be to improve methodological support for the financial security of Ukrainian regions.

Analytical Challenges of Spray Pattern Method Development for Purposes of In Vitro Bioequivalence Testing in the Case of a Nasal Spray Product.

Background: A spray pattern (SP) test is one of the most challenging in vitro tests for nasal spray products (NSPs) associated with a high degree of variation. The total results variation observed in such studies should be in major part representative of product performance to assure high confidence when making conclusions based on obtained results. Analytical methods should be developed in a way to minimize variation contribution of random factors. A systematic statistical assessment of sources of variation is encouraged to be performed during any method development. Methods: This study includes the development of a product-shaking procedure, definition of in vivo relevant actuation parameters, and the development of a robust SP method considering NSP behavior. The final SP method is tested on different days and in different laboratories to evaluate the contribution of individual factors and interactions to the observed variance in SP using a gauge repeatability and reproducibility (GRR) model. Results: It was found that the time lag between consecutive actuations significantly influences the variability of the SP area, suggesting the importance of determining a recovery period. Factor analyst was not found to be important. Factor day was found to have the potential to impact results, mostly through interactions with other factors, suggesting that one should pay attention when performing any comparative studies within the same laboratory on different days. Significant differences were observed when the same product was tested in different laboratories. Conclusion: Key random factors, which significantly contribute to total variation, were identified using a GRR approach. By applying an appropriate control strategy over these factors, one can assure that assessed total variation can be representative of product performance. The same general approach is not only applicable to development of SP method for NSP but to all types of analytical testing as well.

Linking park users' socio-demographic characteristics and visit-related preferences to improve urban parks

The characteristics, behaviors and preferences of urban-park users are seldom gleaned and analyzed to improve park planning and management. This study addresses the research gap using Hong Kong case studies, aiming at four objectives: firstly, to establish socio-demographic profiles of park users; secondly, to evaluate their visit-related preferences; thirdly, to examine the effect of socio-demographic variables on visit-related preferences; and fourthly, to apply the findings to improve urban parks. A questionnaire survey covered 872 users in eight urban parks in four districts. Non-Chinese respondents, married with children and less educated visited parks more often. Users were mainly residents of the district, usually visiting at least once per week, in all four seasons, and preferably in good weather. Three habitual companions were family or relatives, friends, and partner or boyfriend or girlfriend. A factor importance index (FII), summing Cramer's V statistic adjusted by significance level, was computed to indicate relative contributions of individual factors. Six of the 15 socio-demographic variables were significantly associated with visit-related variables, including in order of FII: economic activity status, age, number of children, ethnicity, educational attainment, and marital status. Seven of the ten visit-related variables were significantly associated with socio-demographic variables, including habitual companions, residential years, park-visiting frequency, and familiarity with other park users. The findings allowed formulation of a comprehensive, socially-relevant and community-sensitive strategy to improve urban parks. Applicability of the findings highlighted the pertinence of objective research data to match parks with the leisure and recreational needs of urban residents.

Tribological characterization of recycled basalt-aramid fiber reinforced hybrid friction composites using grey-based Taguchi approach

Fibers play an imperative role in determining the tribological behavior of reinforced friction composites. The objective of the present study is to develop recycled basalt and recycled aramid fiber reinforced hybrid friction composites with the addition of various fillers and optimize the tribological behaviors of the composites. The pin-on-disc test rig was used to conduct dry sliding wear following Taguchi’s L27 orthogonal array with process parameters of the applied load, sliding speed and the weight percentage of fiber content. Grey relational analysis was adopted for tribological parameters optimization, satisfying multiple performance characteristics. Analysis of variance was used to find the contribution of individual factors that affect tribological behavior. Optimal parameter combination for multi-response characteristics of the friction composite under investigation was applied a load of 15 N, sliding speed of 1 m s−1 and composite with 25 weight percent of fiber content. The results showed that addition of fiber content significantly increased wear resistance of the friction composites. Further, from the scanning electron microscopy images of friction and wear tested friction composites, plateau formation, fiber-matrix debonding, fiber pull out, cracks and damage on the matrix and various wear mechanism were identified.

Theoretical Considerations on Factors Confounding the Interpretation of the Oceanic Carbon Export Ratio

AbstractThe fraction of primary production exported out of the surface ocean, known as the export ratio (ef ratio), is often used to assess how various factors, including temperature, primary production, phytoplankton size, and community structure, affect the export efficiency of an ecosystem. To investigate possible causes for reported discrepancies in the dominant factors influencing the export efficiency, we develop a metabolism‐based mechanistic model of the ef ratio. Consistent with earlier studies, we find based on theoretical considerations that the ef ratio is a negative function of temperature. We show that the ef ratio depends on the optical depth, defined as the physical depth times the light attenuation coefficient. As a result, varying light attenuation may confound the interpretation of ef ratio when measured at a fixed depth (e.g., 100 m) or at the base of the mixed layer. Finally, we decompose the contribution of individual factors on the seasonality of the ef ratio. Our results show that at high latitudes, the ef ratio at the base of mixed layer is strongly influenced by mixed layer depth and surface irradiation on seasonal time scales. Future studies should report the ef ratio at the base of the euphotic layer or account for the effect of varying light attenuation if measured at a different depth. Overall, our modeling study highlights the large number of factors confounding the interpretation of field observations of the ef ratio.

Delinquency and drug use among adolescents and emerging adults: The role of aggression, impulsivity, empathy, and cognitive distortions

ABSTRACTRisk behaviors are well known to be higher in adolescents and emerging adults. Drug use and delinquency present several common predictive factors. The aim of the present study was to assess the contribution of individual factors (aggression, impulsivity, empathy, and cognitive distortions) to delinquent behaviors, alcohol use and cannabis consumption among adolescents and emerging adults. Participants were between 15 and 25 years of age (M = 18.64 years, SD = 2.61); 325 were adolescents (15–18 years of age, M = 16.56, SD = 1.11, 56.31% of women) and 283 were emerging adults (19–25 years, M = 21.03, SD = 1.62, 50.88% of women). They completed self-report validated questionnaires. Multiple regression analyses showed that all individual factors significantly predicted delinquency. Impulsivity and empathy significantly predicted alcohol use. Concerning cannabis use, impulsivity is the only significantly associated predictor. Moderation analysis showed that specific associations were stronger in adolescents, whereas others were stronger in emerging adults. All these variables explained 69% of the variance of delinquency, 31% of the variance of alcohol use, and 18% of the variance of cannabis use. This model demonstrated acceptable goodness-of-fit criteria. These results may have implications for prevention and intervention.

The characteristics of evapotranspiration and crop coefficients of an irrigated vineyard in arid Northwest China

Oasis effect may have significant impacts on the crop water use in irrigated fields of extremely arid conditions. Studies on crop coefficients and its relevant influence factors are essential to accurately determine the irrigation scheduling under such conditions. A two-year experiment was conducted in an irrigated vineyard to estimate evapotranspiration (ET) and its two components: evaporation (E) and crop transpiration (T), and to develop appropriate region-specific crop coefficients (Kc, Kcb) in arid Northwest China. The contributions of “oasis effect” to Kc, the relationships of both Kc and Kcb to canopy conductance (Gc) and leaf area index (LAI) were investigated. Local values of Kc for evapotranspiration and crop transpiration (Kcb) were calculated using the field data and the dual-Kc approach. The daily ET ranged from 0.80 to 9.87 mm d−1 and from 0.99 to 8.73 mm d−1 in 2014 and 2015, respectively, with corresponding T/ET values amounting to approximately 58.4% and 55.1%. The locally averaged Kc values were 0.79, 1.31, and 1.08 during the initial, middle, and late growth stages, respectively, versus corresponding Kcb values of 0.17, 0.97, and 0.64. Arid advection accounted for 16.9 to 57.4% and from 1.4 to 49.0% of daily Kc during the two study periods. Both Kc and Kcb to LAI is a linear regression but to Gc is an exponential one. LAI is a better indicator than Gc when it is used to predict Kc and Kcb. These results will help growers to improve irrigation efficiency and quantify the contributions of individual factors to Kc and Kcb in such conditions.

Revealing the Contribution of Individual Factors to Hydrogen Evolution Reaction Catalytic Activity

For the electrochemical hydrogen evolution reaction (HER), the electrical properties of catalysts can play an important role in influencing the overall catalytic activity. This is particularly important for semiconducting HER catalysts such as MoS2 , which has been extensively studied over the last decade. Herein, on-chip microreactors on two model catalysts, semiconducting MoS2 and semimetallic WTe2 , are employed to extract the effects of individual factors and study their relations with the HER catalytic activity. It is shown that electron injection at the catalyst/current collector interface and intralayer and interlayer charge transport within the catalyst can be more important than thermodynamic energy considerations. For WTe2 , the site-dependent activities and the relations of the pure thermodynamics to the overall activity are measured and established, as the microreactors allow precise measurements of the type and area of the catalytic sites. The approach presents opportunities to study electrochemical reactions systematically to help establish rational design principles for future electrocatalysts.

Factors Affecting Nitrogen Use Efficiency and Grain Yield of Summer Maize on Smallholder Farms in the North China Plain

The summer maize yields and partial factor productivity of nitrogen (N) fertilizer (PFPN, grain yield per unit N fertilizer) on smallholder farms in China are low, and differ between farms due to complex, sub-optimal management practices. We collected data on management practices and yields from smallholder farms in three major summer maize-producing sites—Laoling, Quzhou and Xushui—in the North China Plain (NCP) for two growing seasons, during 2015–2016. Boundary line analysis and a Proc Mixed Model were used to evaluate the contribution of individual factors and their interactions. Summer maize grain yields and PFPN ranged from 6.6 t ha−1 to 14.2 t ha−1 and 15.4 kg kg−1 to 96.1 kg kg−1, respectively, and averaged 10.5 t ha−1 and 49.1 kg kg−1, respectively. The mean total yield gap and PFPN gap were 3.6 t ha−1 and 43.3 kg kg−1 in Laoling, 2.2 t ha−1 and 24.5 kg kg−1 in Xushui, and 2.8 t ha−1 and 41.1 kg kg−1 in Quzhou. A positive correlation was observed between the yield gap and PFPN gap; the PFPN gap could be reduced by 6.0 kg kg−1 (3.6–6.6 kg kg−1) by reducing the yield gap by 1 t ha−1. The high yield and high PFPN (HH) fields had a higher plant density and lower N fertilization rate than the low yield and low PFPN (LL) fields. Our results show that multiple management factors caused the yield gap, but the relative contribution of plant density is slightly higher than that of other management practices, such as N input, the sowing date, and potassium fertilizer input. The low PFPN was mainly attributed to an over-application of N fertilizer. To enhance the sustainable production of summer maize, the production gaps should be tackled through programs that guide smallholder farmers on the adoption of optimal management practices.

Types of Perception toward Ethical Issues in Perioperative Nurses: Q-Methodological Approach

This study was aimed at identifying the types of perceptions of ethical issues among perioperative nurses. Q-methodology focusing on individual subjectivity was used with data collected in November 2016. Thirty-four Q-statements were selected and scored by the 35 participants on a 9-point scale with normal distribution. Participants were perioperative nurses working in advanced general hospitals and general hospitals. The data were analyzed using the PC-QUANL program. total of 35 perioperative nurses were classified into 4 factors based on the following viewpoints: self-centered (type 1), onlooking and avoiding (type 2), patient-centered (type 3), and problem-centered (type 4). The 4 factors accounted for 57.84% of the total variance. Individual contributions of factors 1, 2, 3, and 4 were 41.80%, 7.18%, 5.20%, and 3.66%, respectively. The major contribution of this study is the clarification of perioperative nurses' subjective perceptions of ethical issues. These findings can be used in formulating effective strategies for nursing educators, professional nurses, and nursing administrators to improve ethical decision-making abilities and to perform ethical nursing care by the appropriate management of ethical issues in everyday nursing practice.

Observer Variability in CT Perfusion Parameters in Primary and Metastatic Tumors in the Lung.

Purpose:Evaluate observer variability in computed tomography perfusion measurements in lung tumors and assess the relative contributions of individual factors to overall variability.Materials and Methods:Four observers independently delineated tumor and defined arterial input function region of interests (tumor region of interest and arterial input function region of interest) on each of 4 contiguous slice levels of computed tomography perfusion images (arterial input function level), in 12 computed tomography perfusion data sets containing lung tumors (>2.5 cm size), on 2 separate occasions. Computed tomography perfusion parameters (blood flow, blood volume, mean transit time, and permeability surface area product) for tumor volumes of interest were computed for all combinations of these factors, totaling up to 1024 combinations per patient. Overall, inter- and intraobserver variability were assessed by within-patient coefficient of variation, variance components analyses, and intraclass correlation.Results:Overall observer within-patient coefficient of variations for tumor blood flow, blood volume, mean transit time, and permeability surface area product were 20.3%, 11.9%, 6.3%, and 31.7%, and intraclass correlations were 0.94, 0.91, 0.82, and 0.72, respectively. Interobserver tumor volume of interest and arterial input function level were the highest contributors to overall variance for blood flow, blood volume, and mean transit time. Overall intraobserver wCVs for blood flow, blood volume, mean transit time, and permeability surface area product (4.3%, 2.4%, 0.9%, and 3.1%) were smaller than interobserver within-patient coefficient of variations (9.5%, 5.6%, 1.6%, and 7.0%), respectively.Conclusion:The largest contributors to observer variability were interobserver tumor volume of interest and arterial input function level. Overall variability in computed tomography perfusion studies can potentially be minimized by using a single observer and a consistent level for arterial input function, which would be important considerations in longitudinal and multicenter studies. Methods to reliably define arterial input function and delineate tumor volumes would help to reduce variability in estimations of computed tomography perfusion parameter values.