Logit Equation Research Articles

Can a publicly funded home care system successfully allocate service based on perceived need rather than socioeconomic status? A Canadian experience

The present quantitative study evaluates the degree to which socioeconomic status (SES), as opposed to perceived need, determines utilisation of publicly funded home care in Ontario, Canada. The Registered Persons Data Base of the Ontario Health Insurance Plan was used to identify the age, sex and place of residence for all Ontarians who had coverage for the complete calendar year 1998. Utilisation was characterised in two dimensions: (1) propensity - the probability that an individual received service, which was estimated using a multinomial logit equation; and (2) intensity - the amount of service received, conditional on receipt. Short- and long-term service intensity were modelled separately using ordinary least squares regression. Age, sex and co-morbidity were the best predictors (P < 0.0001) of whether or not an individual received publicly funded home care as well as how much care was received, with sicker individuals having increased utilisation. The propensity and intensity of service receipt increased with lower SES (P < 0.0001), and decreased with the proportion of recent immigrants in the region (P < 0.0001), after controlling for age, sex and co-morbidity. Although the allocation of publicly funded home care service was primarily based on perceived need rather than ability to pay, barriers to utilisation for those from areas with a high proportion of recent immigrants were identified. Future research is needed to assess whether the current mix and level of publicly funded resources are indeed sufficient to offset the added costs associated with the provision of high-quality home care.

The relationship between severity of obstructive sleep apnoea/hypopnoea syndrome (OSAHS) and lateral cephalometric radiograph values: A clinical diagnostic tool

This prospective cross-sectional cohort study examined the relationship between radiographic anatomy and the severity of OSAHS. The severity of OSAHS can be measured subjectively in terms of the Epworth scale and objectively in terms of the apnoea/hypopnoea Index (AHI). 121 lateral cephalometric radiographs were traced under uniform conditions and a series of 56 landmarks identified, from which 48 angular and linear measurements were made. Significant changes occurred when comparison of these measurements with the severity of OSAHS were made. Body mass index (BMI), the maxillary-mandibular planes angle (MMPA) and the linear measurement between points 7 and 12, (the pharyngeal dimension measured from the tip of the soft palate to the corresponding horizontal point on the posterior pharynx), increased significantly with increasing severity of OSAHS as measured by the Epworth score. Overjet, lower lip length, and the distance from the hyoid bone to a point B on the mandible all increased significantly with increasing severity of OSAHS, as measured by the AHI. The hyoid bone was found to rotate counter clockwise as the severity of OSAHS increased, as a result the distance between the most anterior superior point on the hyoid bone and the maxillary plane was seen to decrease as severity of OSAHS increased in terms of AHI. Some radiographic anatomical features show significant change as the severity of OSAHS increases and these features could be used in the identification of patients who have severe OSAHS. The Logit equation derived from the findings of this study may also be a useful clinical tool in predicting the likelihood of a subject suffering from severe OSAHS.

AIDS education, condom demand, and the sexual activity of American youth

This paper examines the effects of AIDS education at school and at home on the sexual behavior of American youth. Multinomial logit equations of the probabilities of abstinence, sexual intercourse with a condom, and intercourse without a condom are estimated using data from the Youth Risk Behavior Supplement of the 1992 National Health Interview Survey. We find no significant effects of AIDS education on the probability of abstinence, but we do find that AIDS education significantly raises the likelihood of condom-protected relative to unprotected intercourse. These results indicate that risk-altering and risk-revealing AIDS education dominate any utility-altering effects favoring intercourse over abstinence. We also find that young women are influenced by AIDS education to a greater extent than young men. Overall, our results suggest that educating young people about AIDS does not promote sex and encourages safer sex, reducing the likelihood of HIV transmission and lowering the subsequent social costs.

Monetary operations by Hong Kong's Currency Board

Currency Boards are typically seen as demonstrating the advantages of rule-bound monetary policies with automatic responses to exchange market imbalances. We study the monetary operations conducted by Hong Kong's Currency Board, using daily data between September 1998 and December 2001. Since this regime is one-sided in that there is a commitment to sell, but not to buy, US dollars at a given rate, we estimate logit equations for dollar purchases. We show that these have shifted over time and that while the variables are statistically highly significant, the predictive power is low.

Socioeconomic status and health among older adults in rural and urban China.

The association between socioeconomic status (SES) and health, which has proven to be quite robust, is rarely tested in societies where levels of economic development and systems of stratification differ from those in Western developed countries. This article examines associations in rural and urban China. Techniques include logit equation estimates of separate and pooled samples. The latter employ interaction terms to test rural and urban effects. Socioeconomic indicators include those more customarily used in these types of studies (e.g., education) and several that are less traditional (e.g., pension eligibility). Results indicate associations exist in China. Bank savings is the strongest predictor. Some unexpected results are also found, including a positive association between socioeconomic status and chronic conditions (e.g., cardiovascular disease) among older adults in urban China. Use and access to a health care professional might explain part of this anomaly.

Estimating Latent Structure Models with Categorical Variables: One-Step Versus Three-Step Estimators

We study the properties of a three-step approach to estimating the parameters of a latent structure model for categorical data and propose a simple correction for a common source of bias. Such models have a measurement part (essentially the latent class model) and a structural (causal) part (essentially a system of logit equations). In the three-step approach, a stand-alone measurement model is first defined and its parameters are estimated. Individual predicted scores on the latent variables are then computed from the parameter estimates of the measurement model and the individual observed scoring patterns on the indicators. Finally, these predicted scores are used in the causal part and treated as observed variables. We show that such a naive use of predicted latent scores cannot be recommended since it leads to a systematic underestimation of the strength of the association among the variables in the structural part of the models. However, a simple correction procedure can eliminate this systematic bias. This approach is illustrated on simulated and real data. A method that uses multiple imputation to account for the fact that the predicted latent variables are random variables can produce standard errors for the parameters in the structural part of the model.

Understanding data in clinical research: a simple graphical display for plotting data (up to four independent variables) after binary logistic regression analysis

In clinical research, suitable visualization techniques of data after statistical analysis are crucial for the researches’ and physicians’ understanding. Common statistical techniques to analyze data in clinical research are logistic regression models. Among these, the application of binary logistic regression analysis (LRA) has greatly increased during past years, due to its diagnostic accuracy and because scientists often want to analyze in a dichotomous way whether some event will occur or not. Such an analysis lacks a suitable, understandable, and widely used graphical display, instead providing an understandable logit function based on a linear model for the natural logarithm of the odds in favor of the occurrence of the dependent variable, Y. By simple exponential transformation, such a logit equation can be transformed into a logistic function, resulting in predicted probabilities for the presence of the dependent variable, P( Y=1). This model can be used to generate a simple graphical display for binary LRA. For the case of a single predictor or explanatory (independent) variable, X, a plot can be generated with X represented by the abscissa (i.e., horizontal axis) and P( Y=1| X) represented by the ordinate (i.e., vertical axis). For the case of multiple predictor models, I propose here a relief 3D surface graphic in order to plot up to four independent variables (two continuous and two discrete). By using this technique, any researcher or physician would be able to transform a lesser understandable logit function into a figure easier to grasp, thus leading to a better knowledge and interpretation of data in clinical research. For this, a sophisticated statistical package is not necessary, because the graphical display may be generated by using any 2D or 3D surface plotter.

The economic model of divorce: the neglected role of search and specific capital formation

The present paper uses a large national survey, from the UK to estimate a logit equation for the probability of ever having been divorced within a population of those who have ever been married. The survey utilized permits the construction of several variables, not hitherto deployed in econometric work, which measure aspects of partner search and relationship capital formation. The results indicate that these things are important with there also being notably different results for men and women.

A logit analysis of vehicle emissions using inspection and maintenance testing data

Many states use vehicle inspection and maintenance (I/M) programs to identify high polluting vehicles and ensure that they operate in accordance with standards. While I/M programs are generally regarded as a valuable means to curb urban air pollution, they have been often criticized for their cost-ineffectiveness. One criticism has been centered on the blanket approach that requires all vehicles within the program boundaries to participate regardless of their emission conditions. This paper explores the basis for a selective sampling of vehicles most likely to be pollution violators. Using I/M testing data from Portland, Oregon, it estimates logit equations for the likelihood of carbon monoxide and hydrocarbon emission violations given a set of vehicle characteristics. The results indicate that vehicle age, engine size, and odometer reading all play a significant role in determining the probability of emission test failure.

Language‐Related Differences in a Contingent Valuation Study: English Versus Spanish

AbstractTo test the similarity of English‐ and Spanish‐speaking households responses to a contingent valuation survey, phone interviews were conducted in both languages regarding two forest fire prevention programs. While there were similar response rates, there were significant differences in the most frequent reasons given for refusing to pay. In the pooled logit model, the language intercept and bid interaction variables were insignificant in both programs. The likelihood ratio test of separate logit equations showed no statistical difference between English‐ and Spanish‐speaking households responses to either program. Mean benefits reported by Spanish‐speaking households were about one‐third lower than English‐speaking households, although the difference is not statistically significant.

Increase in the prevalence of allergen skin sensitization in successive birth cohorts.

Little is known about longitudinal trends in the prevalence of allergen skin sensitization in the general population. We sought to measure the change in prevalence of allergen skin sensitization over a 9-year period in a cohort of adults and hence to determine whether cross-sectional differences in prevalence between age groups are due to an aging or cohort effect. In 1991 and 2000, we measured skin sensitization, defined as a wheal diameter of 3 mm or larger than that elicited by a saline control, to Dermatophagoides pteronyssinus, cat fur, mixed grass, Aspergillus fumigatus, and Cladosporium herbarum in a cohort of 1339 adults from Nottingham aged between 18 and 71 years in 1991. Subjects were divided into six 9-year successive birth cohorts, and the effects of birth cohort and the within-subject change from 1991 to 2000 were analyzed in a generalized estimating equation logit model. The unadjusted prevalence of sensitization to any allergen was 30.5% in 1991 and 31.8% in 2000. In cross-sectional analyses the prevalence of sensitization decreased with increasing age at both surveys (risk ratio, 2.15; 95% confidence interval [CI], 1.45-3.17 for 18- to 26-year-old patients relative to 63- to 70-year-old patients in the 1991 survey). In longitudinal analysis there was no within-subject change in sensitization from 1991 to 2000 (adjusted odds ratio, 1.07; 95% CI, 0.97-1.19), but there was a significant cohort effect (adjusted odds ratio per successive 9 year cohort, 1.27; 95% CI, 1.18-1.37). The cross-sectional decrease in allergen sensitization with age in the general population arises predominantly from a secular increase in sensitization prevalence with successive birth cohorts and not to a loss of sensitization within subjects over time. As a result of this cohort effect, the prevalence of allergic sensitization has increased in this general adult population sample.

The economic analysis of social customs: the case of pre-marital sex

This paper uses a sample of 18,876 adults aged 16-59 from to estimate logit equations of the determinants of support for the custom of abstaining from pre-marital sex. Three sets of equations are estimated separately for males and females; one set for disapproval of pre-marital sex, one set for disapproval of one night stands and another set for a proxy for involvement in pre-marital sex. These results confirm some expected male-female differences and also show a polarisation amongst the population in their support for, and observance of, customs and practices related to abstaining from sex before marriage.

Surrender Value of Capital Assets: The Economics of Strategic Virginity Loss

This paper provides the first econometric analysis of rationalizations of virginity loss in terms of love. Data from the UK National Survey of Sexual Attitudes and Lifestyles are used to estimate logit equations to predict the claim that virginity loss was occasioned by being in love. The sample consists of 2,269 males and 1,476 females between the ages of 16 and 59. In economic terms, a dichotomy is found in terms of male and female virginity loss, such that to a degree it is possible to infer that sex is for males more of a consumption good, whilst for females it is more of a capital good.

Predictive Value of Cord Blood Hematological Indices and Hemoglobin Barts for the Detection of Heterozygous α-Thalassemia-2 in an African-Caribbean Population

Cord blood hemoglobin Barts (HbBarts) and hemocytometric indices may be used for classification of newborns into those without alpha-thalassemia-2 (alphaalpha/alphaalpha) and with heterozygous alpha-thalassemia-2 (-alpha(3.7)/alphaalpha). We investigated by logistic regression analysis whether the combination of HbBarts and hemocytometric indices improves classification compared with classification based on a single analyte. HbBarts percentages and hemocytometric indices were determined in cord blood of 208 consecutive newborns in Curaçao (Netherlands Antilles). Of these, 157 had alphaalpha/alphaalpha and 51 had -alpha(3.7)/alphaalpha, as established by DNA analysis. Between-group differences were significant for erythrocytes, mean cell volume, mean cell hemoglobin (MCH), mean cell hemoglobin concentration, platelets, hemoglobin F(0) (HbF(0)), and HbBarts. The Logit equation of the logistic regression model, using MCH (pg) and HbBarts (%), was: 42.7164 + 5.7916(HbBarts) - 1.3110(MCH). A sensitivity of 100% was reached at a Logit value of -3.70. The corresponding specificity was 62.2%, and the predictive value of a positive test (PV+) was 46.3% (95% confidence interval, 37.0-55.7%). The relative information gains were as follows: 88% for the HbBarts-MCH combination, 26% for MCH (not significant), and 0% for HbBarts compared with the 24.6% -alpha(3.7)/alphaalpha prevalence. Combined use of cord blood HbBarts and MCH improves classification compared with classification based on single hemocytometric indices.

Employment equity and minority legislation in the UK after two decades: a review

Examines employment equity legislation, initially introduced in the UK during the 1970s, along with separate legislation covering sex, race, religion and disability, together with separate enforcement bodies, and separate geographical arrangements in Britain and in Northern Ireland. Notes the role of European Community Law which takes precedence over UK law and increasingly dictates legislation changes. Claims that the period since the 1970s has witnessed growing levels of unemployment, along with a focus on de‐regulation of labour markets. Most British empirical work focuses on explaining earnings differentials using the standard Mincer human capital model with comparative neglect of employment equality issues. The fundamental question is to what extent has employment equity legislation been successful in removing labour market discrimination against minority groups. Uses a cross‐section of data from the 1994 labour force survey to attempt to explain differences in employability across various groups and to analyse the degree of occupational segregation across these same groups which remain after nearly 20 years of experience of employment equity legislation. Reviews the legislation and then estimates first, logit equations to explain employability and second, ordered probit equations to explain occupational attainment, in each case decomposing the results in order to estimate the proportion of the differential which may be explained by “discrimination”.

The effect of incremental benefit levels on births to AFDC recipients

We examine the relationship between fertility and incremental AFDC benefits using the 1990 Panel of the Survey of Income and Program Participation (SIPP). Estimating a logit equation for the probability of a higher-order birth among a sample of AFDC recipients, we find a positive coefficient (although statistically insignificant) on the incremental AFDC benefit level. However, we find a positive correlation between incremental benefits and fertility for several nonrecipient comparison groups which is larger than the positive correlation for AFDC recipients. This finding suggests that the previously estimated relationship between incremental benefits and fertility among AFDC recipients is largely the result of a spurious correlation. We find similar results among whites, blacks, and never-married women, but less consistent results among Hispanics and divorced or separated women. We infer from these results that family cap policies, which eliminate the incremental benefits entitled to AFDC recipients who have additional children, are not likely to result in a large reduction in the number of out-of-wedlock births to AFDC recipients.

Modelling and analyzing density‐dependent population processes: Comparison between wild and laboratory strains of the bean weevil, Callosobruchus chinensis (L.)

AbstractThree models were constructed for analyzing the population characteristics of C. chinensis on stored beans; model A describing the whole reproductive process with a single equation, model B describing the three age‐specific processes (oviposition, egg survival and larval survival) with separate equations, and model C which describes all these processes not for the whole habitat but for the individual beans comprizing it. The logit equation was employed here as a common basis to describe the density‐response relationship involved. All three models showed very good fit to the experimental data obtained for both laboratory and wild strains of the weevil. The parameter values characterizing the population dynamics were, however, widely different between the two strains; the laboratory one which had been reared for some 500 generations showed significantly higher reproductive capacity, less sensitive and gentler response to crowding in both adult and egg stages, and more uniform egg distribution among individual beans, as compared with the wild strain newly introduced. Sensitivity analyses using these models suggested that these changes in population characteristics have been attained by the process of domestication or adaptation to stable laboratory conditions through a long period of time. This process seemed in effect to have optimized the population's performances in the laboratory environment. Evolutionary significance of such optimization was discussed with reference to the selection pressure which may have acted upon individuals.

Detecting and Correcting Attrition Bias in Longitudinal Family Research

Conducting longitudinal research has been encouraged among family scholars as a way to better understand family process and to measure changes in family structure and relationships over time. When doing longitudinal research, a common problem is the loss of sample members between the first wave of data collection and subsequent waves. Some subjects move between data points and cannot be located, whereas others refuse to continue their participation. Some members of the original sample, especially if it includes older adults, will have died or have become too disabled to participate further in the study. These losses represent an attrition of the original sample over time. These various forms of attrition of a sample result in a potential threat of bias if those who drop out have unique characteristics such that the remaining sample ceases to be representative of the original sample. This bias, known as attrition bias, is assumed to exist when there are significant differences between the initial and later samples. Because the loss of sample members between the first wave of data collection and subsequent waves is relatively common, researchers in longitudinal studies should check for attrition bias. Unchecked bias may be the major threat to longitudinal research (Markides, Dickson, & Pappas, 1982; Norris, 1985). Larzelere and Klein (1987) listed sample attrition as one of the three major problems that researchers face in analyzing longitudinal data. Despite the threat of attrition bias, however, it has received little attention in longitudinal family research. Indeed, few family researchers address this issue when reporting the results of their analyses of longitudinal data. There are two ways attrition can bias a sample. Firs, it may alter the characteristics of the sample, making it no longer representative of the original sample. Because the results of later waves of data are not generalizable to the original population that was sampled, the external validity of the study is threatened. For example, a longitudinal study examining the effects of divorce on the mental health of former spouses may fail to retain those subjects who have become too depressed to respond to the questionnaire. The nonparticipation of this subsample could bias the findings towards a minimization of depression as an outcome of divorce. The second way that selective attrition can bias longitudinal data is by altering the covariance of variables (Goudy, 1985; Norris, 1987). This problem occurs when the underrepresentation of some groups in the longitudinal sample leads to correlations between variables that are different than the true correlations in the original sample. Referring back to the previous example, the underrepresentation of depressed people in the second wave of the study may distort the statistical relation between length of marriage and depression. This poses a potentially severe threat to theory building because of the effect of these distortions on internal validity. TESTING FOR ATTRITION BIAS The most common method for detecting attrition bias in the characteristics of the sample is to use t tests to compare those subjects who responded to all waves of the study with those who dropped out after only one wave. The means of important variables from the first wave, such as socioeconomic status (SES), age, marital satisfaction, and depression, are compared between the two samples to determine if the differences are statistically significantly different. Significant differences in the means of one or more variables indicates the existence of attrition bias. Differences in categorical variables, such as race and marital status, can be determined by using the chi-square statistic. Logit analysis is a second method for detecting differences in characteristics of the sample. A logit equation is developed to estimate the probability that each first wave respondent will participate in later waves. …

State Economies and State Taxes: Do Voters Hold Governors Accountable?

Theory: States have sufficient autonomy in the policies they adopt that voters hold state officials partly responsible for the condition of the state economy. As the best known state official, elected by a statewide constituency, governors in particular are held accountable for the economic performance of their states. With respect to taxes, the clear locus of responsibility in state actions and the high visibility of certain taxes suggest that governors will also be held responsible for increased rates. Hypotheses: The performance of the state economy, tax increases, and voters' personal financial situations all influence voting behavior in gubernatorial elections. Methods: Logit equations, using 1986 ABC/Washington Post exit polls in 34 of 36 gubernatorial races, combined with economic and tax data from the states. Results: A poor state economy, increases in taxes, and lowered personal finances all contribute to votes against incumbent governors and their parties.

Do Reminders of Substitutes and Budget Constraints Influence Contingent Valuation Estimates?

A test is performed of the recommendation by the NOAA panel on contingent valuation that respondents be reminded about other substitute resources and their budget constraint prior to answering the willingness-to-pay (WTP) question. The context for this experiment is a CVM study of the benefits from reducing fire hazards to old-growth forests in Oregon. The test was performed using two mail surveys that were otherwise identical except for the inclusion of reminder statements prior to the WTP question. The dichotomous choice logit equations were not statistically different between versions and the mean WTP results were identical.