Terms Of Percentiles Research Articles

Relation of successive percentiles of reaction time distributions to cognitive variables and adult age

The reaction time distributions for each individual in a moderately large sample of adults were analyzed in terms of percentiles, and then each reaction time percentile was correlated with a number of cognitive variables and with age. A very similar pattern was evident across five sets of reaction time tasks. This consisted of the correlations with the cognitive variables remaining stable, but those with adult age decreasing, from the fastest to the slowest responses emitted by the individual. Contrary to recent reports (Kranzler, 1992; Larson & Alderton, 1990), these results suggest that all portions of the reaction time distribution contain qualitatively similar individual difference information.

A clinical and academic outcome study of children attending a day treatment program.

To assess the behavioural and academic improvement of children who attended a day treatment program during a defined period of time. Forty-six children admitted consecutively to the project were assessed on admission and discharge using behavioural and academic measures. They also had intelligence and language assessments. The subjects attended the program for one academic year, on the average. The large majority presented with disruptive behaviour disorders and low academic achievement levels. There was a significant improvement reported by the parents in externalizing (P < 0.001) and internalizing (P < 0.05) behaviour. The subjects also gained one academic year, but their levels continued to be low in terms of percentiles. Measures of academic improvement showed significant associations with cognitive measures only (subscales of Wechsler Intelligence Scale for Children-Revised [WISC-R] and Clinical Evaluation of Language Fundamentals-Revised [CELF-R]). A day treatment and school program is an effective modality for treatment and remediation of children with severe psychiatric disorders. The academic underachievement may be resistant to remediation within the limited period of attendance in such a program.

Coefficient of variation as a measure of relative wetness of different stations in India

Assessment of relative wetness in different months is a prerequisite for proper planning and utilization of available water resources of an area. Using monthly rainfall data of four different stations in India, the present paper shows thatCv, the coefficient of variation, can be used as a measure of relative wetness/dryness. It was further observed that the amount of rainfall for a given probability level can be quickly computed in terms of percentile values.Cv is exponentially related to P60, the sixtieth percentile of the amount of rainfall.

The College Plans of Academically Talented Students

Academically talented students scoring in the 95th and 99th percentiles on the 1986 ACTs were compared to each other and to “high average” students scoring in the 80th percentile in terms of their choices for college majors, extracurricular plans, and desires for services. Academically talented students were found to be narrow in their choices of majors but broad in their extracurricular interests. Although uninterested in personal counseling, they are demanding of career counseling, independent study, and honors opportunities.

Group Scores: A Rejoinder to Burket

Dr. George Burket and I appear agree on the existence of a problem in the calculation and interpretation of group scores on norm-referenced tests, but we part company on the issue of that problem's causes and solutions. His comment (Burket, 1987) contains some fine measurement theory and insightful observations, particularly in the final three paragraphs. However, these paragraphs are in large part irrelevant the one point in the article that Burket especially controverts, namely my suggestion that publishers' scaled score development procedures may be largely responsible for the sorts of problems identified. Other portions of the comment, which are relevant this controverted point, challenge ideas that I offered hypotheses and as a basis for (Baglin, 1986, p. 65) in a section titled Why Does This Phenomenon Occur? However, nothing in the comment has caused me retract or modify this hypothesis or, for that matter, any of the original article. Quite the contrary, the absence in the comment of any substantive discussion, much less rebuttal, of my hypothesized cause and suggested solutions leads me strengthen my contention that a large share at least of the culpability for this problem lies precisely with the publishers' scaled score development procedures. Four points in the comment should be clarified. First, the statement is made that in the normative distributions makes possible the problem described at the outset in Baglin's paper, where a local mean falls below the national mean yet is well 'above average' in terms of percentiles (i.e., above the median) (Burket, 1987, pp. 175-176). This could be, theoretically, a full or partial explanation of the phenomenon I cited if the original raw score normative distribution had been positively skewed. But, as is noted in the article, that distribution was negatively skewed, thus making Burket's statement untenable. Second, it is stated the the apparent discrepancies ... noted by Baglin ... result from basic mathematical facts (Burket, 1987, p. 175), one of which is identified as the asymmetry issue discussed above. Because the asymmetry explanation is inaccurate, it follows that this further contention is also inaccurate. Third, the comment contends that it is possible come close in an effort to simultaneously transform two or more distributions perfect normality on the same baseline (Burket, 1987, p. 175) and cites my Table 7 as evidence. This is selective use of data. Tables 4, 8, and 9 show analogous maximum discrepancies of up 10 times the magnitude of the one chosen as an example. It should not be inferred or implied that the Table 7 situation is typical or even common. Fourth, the comment's Table 1 and associated discussion deal exclusively with individual scores, not with group scores, which are the topic of my article. Furthermore, the percentile and NCE derived scores therein are straightforward computations based on the raw scores-a variant of what I suggested in the original article's

Reliability Bounds for Fault-Tolerant Systems with Competing Responses to Component Failures

Bounds are established for the probability of failure of fault-tolerant systems. The underlying failure and recovery process is assumed to follow a semi-Markov model in which the potential sojourn times of component failures have exponential distributions and those of system responses have general distributions. A product form of the bounds is derived from a model which provides for competing responses to component failures. Bounds are calculated in terms of integral factors which depend on component failure rates and the actual distributions of response times. Bounds are also calculated in terms of percentiles, conditional mean response times, and certain transition probabilities. Besides providing a computationally efficient method of estimating reliability from a flexible model, the bounds seem reasonably tight for a fairly wide range of cases. An example is given to illustrate calculating the bounds for a model with competing system responses.

Skewness properties of asymmetric foems of tu1cey lambda distributions

Some measures of skewness are the third central moments the mean minus the median, arid measures in terms of percentiles. The signs of these measures are analysed for two asymmetric generalisations of Tukey's lambda distribution. The results expand and explain some results of Ramberg et al.1979, and illustrate the problem of choosing an appropriate measure of skewness.

Physical growth of pre-pubertal Punjabi girls

Cross-sectional data on 724 pre-pubertal Punjabi girls ranging in age from 6 to 12 years, were collected from the primary sections of various schools of Patiala city during 1974. Children belonging to the lower and lower-middle socio-economic groups were included in the present study. Nine anthropometric measurements including three skinfolds were taken on each subject. Statistical constants like mean, standard deviation and standard error of mean have been calculated. Growth standards of girls in terms of percentiles for these age groups have been constructed for some selected measurements. The resluts show that the velocity of weight increases in the successive ages up to 10–11 years. All other anthropometric measurements excluding skinfolds, show a general trend of decline in the rate of growth of body measurements up to 10–11 years. The girls ef this sample seem to pick up accelerated growth during the 11–12 year age interval to enter the adolescent growth spurt. The pattern of change of subcutaneous tissue provides two types of pictures-suprailiac and subscapular skinfolds show continuous increase during the period under study whereas the triceps skinfold decreases up to 9 years and again increases. The velocity curves of the skinfolds do not indicate any appreciable trend of increase or decrease. Linear regression equations were fitted to height, weight, log weight, and sitting height measurements. It is noticed that log weight measurements provide a better fit upon age than the weight measurements taken as such.

The normal metacarpal index

Normal values for the metacarpal index (MCI) in British children and adults have been determined. In infancy before the appearance of the metacarpal epiphyses the index is constant up to about two years of age (5.2 in males and 5.5 in females). During childhood the index rises to reach a peak at about 16 years, and then falls slightly during adult life. The curves produced are almost identical to those previously found in black children, and one set of values may be used for children of either ethnic origin. The left hand should be used to calculate the MCI, and the results expressed as either below the mean for age, or in terms of percentile for age above the mean. Curves are presented showing percentile values. No attempt should be made to produce a clear distinction between normal and abnormal indices, but the percentile value used in conjunction with other clinical findings in the assessment of Marfan's syndrome and other skeletal conditions associated with arachnodactyly.

INFANT BEHAVIOUR

<h3>Abstract</h3> <h3>Background</h3> Long COVID—also known as post-acute sequelae of COVID-19 or PASC—is a systemic syndrome affecting a large number of persons in the aftermath of the pandemic. Cognitive dysfunction (or brain fog) is one of its most common manifestations of PACS, and there are no effective interventions to mitigate it. Home-based personalized computerized cognitive training (CCT), which has shown effectiveness to improve other conditions, could offer hope to relieve the cognitive dysfunction in people with a previous history of COVID-19. <h3>Objective</h3> To evaluate the feasibility and potential benefit of a personalized CCT intervention to improve cognitive function among people living with PACS. <h3>Methods</h3> Adult individuals who self-reported cognitive dysfunction more than 3 months after a diagnosis of COVID-19 were recruited through an online platform designed for the study. Those who were eligible assessed their general cognitive function before completing as many cognitive daily training sessions as they wished during an 8-week period, using a personalized CCT application at home. The sessions included gamified tasks that tapped into five cognitive domains (attention, coordination, memory, perception and reasoning) and were tailored to the specific cognitive strengths and weaknesses detected at each point. At the end of this period, participants repeated the general cognitive function assessment. The differences between the scores at 8 weeks and baseline was the main outcome, complemented with analyses of the changes based on the participants’ age, training time, self-reported health level at baseline and time since the initial COVID-19 infection. Participants’ cognitive assessment scores were also computed in terms of percentiles according to the normative database of the test, considering their corresponding age- and gender-based reference sample. <h3>Results</h3> The participants had significant cognitive dysfunction at baseline, even though 80% of them had had the initial episode of COVID-19 more than a year before enrolling in the study. Eighty nine percent reported negative levels of self-reported health at baseline. On average, 51 training sessions (range: 10 to 251) were completed over a mean time of 435 minutes (range 78 to 2448). Most of the participants obtained higher scores after CCT in each of the domains as compared with baseline (attention: 81% of the sample; memory: 86%; coordination: 82%; perception: 88%; reasoning: 77%). The magnitude of the score increase at post-test was high across domains (attention: 31% of change; memory: 37%; coordination: 52%; perception: 42%; reasoning: 26%). Following CCT, there were also improvements in the percentile data in all the domains (attention: 14 points; memory: 18 points; coordination: 18 points; perception: 17 points; reasoning: 11 points). <h3>Conclusions</h3> This study suggests that a self-administered CCT based on gamified cognitive tasks could be an effective way to ameliorate cognitive dysfunction in persons with PASC.

The normal variability of the electrocardiogram as a basis for differentiation between “normal” and “abnormal” in clinical electrocardiography

The sources of electrocardiographic variability are discussed in regard to their effect on the diagnostic differentiation between healthy individuals and patients with cardiac pathology. The principles involved are illustrated by the frequency distribution in a sample of healthy men and a sample of patients with posterior wall infarct. Due to skewness of the frequency distributions in some electrocardiographic items, normal limits should be expressed in terms of percentiles, not of means ± multiples of standard deviation. Such limits are presented for normal young and normal older men, together with a weight correction for electrocardiographic standards. For unipolar limb leads, normal limits with correction for the electrical position are given. Data on other sources of variability are presented, including the error of measurement and day-to-day variability.

The norm concept and cephalometrics

1. 1. Most available cephalometric norms describe faciodental traits with reference to the variability of the trait in a population. 2. 2. Clinical use of these norms is thus appropriate for describing or ranking the patient in terms of the norm. It is abusing the norm to use it alone for evaluation in diagnosis, or to use the average as an objective in treatment planning. A norm is not a substitute for professional judgment. 3. 3. A norm is not a single value, but a range of values. Thus, norms constructed in terms of percentiles, such as the ones used in height and weight norms, have certain advantages. They are easy to use and understand. They are usable whether there is a normal or an asymmetrical distribution. Since variability is emphasized, use of percentiles probably reduces a natural tendency to think of the average as a treatment goal. 4. 4. Until we can construct a larger body of knowledge, our normative use of present cephalometric data should recognize some limitations. Sample sizes of most studies are too small to represent fully the variability of a population. Also, the samples have usually been subjectively selected; for example, on the basis of normal occlusion. The importance of this, as well as differences due to age, sex, and race, is yet to be adequately explored. 5. 5. When using cephalometric data, it is very important to recognize that two persons will seldom duplicate each other exactly in tracing or measuring. Individual orthodontists, and also the same orthodontist on different occasions, will often disagree by several degrees. 6. 6. There is such wide variability between individual persons that most cephalometric measures are not diagnostic within themselves. It is abusing normative data to set arbitrary diagnostic limits of abnormality at one or even two standard deviations from the mean. 7. 7. Some children with normal occlusion will have angulation measurements similar to the malocclusion cases. Many aspects of facial pattern do not appear to be related to the presence of a good occlusion or a malocclusion. 8. 8. Individual deviations from the average pattern of growth are marked. Thus, the ability to predict facial growth in different persons varies considerably and does not provide a stable basis for treatment planning on the basis of present knowledge for the period between the ages of 5 years and 13 years.