The relation of item difficulty and inter-item correlation to test variance and reliability

Under assumptions that will hold for the usual test situation, it is proved that test reliability and variance increase (a) as the average inter-item correlation increases, and (b) as the variance of the item difficulty distribution decreases. As the average item variance increases, the test variance will increase, but the test reliability will not be affected. (It is noted that as the average item variance increases, the average item difficulty approaches .50). In this development, no account is taken of the effect of chance success, or the possible effect on student attitude of different item difficulty distributions. In order to maximize the reliability and variance of a test, the items should have high intercorrelations, all items should be of the same difficulty level, and the level should be as near to 50% as possible.The desirability of determining this relationship has been indicated by previous writers. Work on the present paper arose out of some problems raised by Dr. Herbert S. Conrad in connection with an analysis of aptitude tests.On leave for Government war research from the Psychology Department, University of Chicago.     

Development of planning and its relation to other cognitive processes

The purpose of this study was to (a) delineate the course of development of children's planning skills during school years, (b) examine whether different levels of planning exist, and (c) explore the role of other cognitive processes as cognitive correlates of planning. The participants were 250 students, 50 from each of the five targeted grades (3, 5, 7, 9, and 11). They each completed a battery of planning, attention, and simultaneous and successive processing tasks. MANOVA indicated that the main effect of grade was significant, whereas gender had no significant effect on planning. Pairwise comparisons of performance means between grades indicated that developmental trajectories were not uniform across planning tasks. Correlation and regression analyses showed that the relationship between planning tasks and attention, and simultaneous and successive processing scores varied as a function of the planning task and the grade level. Furthermore, two planning factors were found and cluster analyses of variables indicated that one of the tasks, Crack-the-Code, may represent a different kind of planning than the other planning tasks used.     

The correlation of EPQ psychoticism with two behavioural measures of impulsivity

The Psychoticism (P) scale of the Eysenck Personality Questionnaire (EPQ) was correlated with performance on two behavioural measures of impulsivity: total number of Errors in a choice reaction-time (RT) task, and number of Taboo Responses in an open-ended creativity test. Experiment 1 employed 20 Ss in an auditory RT situation and using an untimed creativity test. P correlated strongly and positively with a logged Taboo Responses measure but not with a logged Errors score. The correlation of P with Errors reached statistical significance when the biserial correlation of P with Errors/No Errors was calculated. Experiment 2 employed 35 Ss in a visual choice RT situation and using a timed creativity test. Questionnaire scales of Venturesomeness, Impulsiveness and Empathy were also used. Both behavioural indices were significantly correlated with P, but not with Venturesomeness or Impulsiveness. The results constitute further support for the view that the P scale of the EPQ contains a strong impulsivity component.     

The relation between measures of cognitive and motor functioning in 5- to 6-year-old children

Specific relations between executive functions (working memory capacity, planning and problem-solving, inhibitory control) and motor skill performance (anticipatory motor planning, manual dexterity) were examined in 5- to 6-year-old children (N = 40). Results showed that the two motor skill components were not correlated. Additionally, it was found that response planning performance was a significant predictor of anticipatory motor planning performance, whereas inhibitory control and working memory capacity measures were significant predictors of manual dexterity scores. Taken together, these results suggest that cognitive and motor skills are linked, but that manual dexterity and anticipatory motor planning involve different specialized skills. The current study provides support for specific relations between cognitive and motor performance, which has implications for early childhood cognitive-motor training and intervention programs.     

Variable criteria sequential stopping rule: Validity and power with repeated measures ANOVA,multiple correlation,MANOVA and relation to Chi-square distribution

The variable criteria sequential stopping rule (vcSSR) is an efficient way to add sample size to planned ANOVA tests while holding the observed rate of Type I errors, α_o, constant. The only difference from regular null hypothesis testing is that criteria for stopping the experiment are obtained from a table based on the desired power, rate of Type I errors, and beginning sample size. The vcSSR was developed using between-subjects ANOVAs, but it should work with p values from any type of F test. In the present study, the α_o remained constant at the nominal level when using the previously published table of criteria with repeated measures designs with various numbers of treatments per subject, Type I error rates, values of ρ, and four different sample size models. New power curves allow researchers to select the optimal sample size model for a repeated measures experiment. The criteria held α_o constant either when used with a multiple correlation that varied the sample size model and the number of predictor variables, or when used with MANOVA with multiple groups and two levels of a within-subject variable at various levels of ρ. Although not recommended for use with χ² tests such as the Friedman rank ANOVA test, the vcSSR produces predictable results based on the relation between F and χ². Together, the data confirm the view that the vcSSR can be used to control Type I errors during sequential sampling with any t- or F-statistic rather than being restricted to certain ANOVA designs.     

Self-reported measures of appetite in relation to verbal cues about many foods

In the present study a representative sample of students from a general college population were exposed to a list of written food cues and asked to rate each of the foods according to its nutritional value. Subjects who were exposed to the food list subsequently reported increases in hunger, desire to eat, and number of foods currently hungry for, as well as reduced fullness, compared to controls who were not exposed to the food list. Also, there was a trend for the food-cued subjects to report hunger for lower fat foods compared to the controls. The results are discussed in terms of previous research and suggestions for future research are provided.     

Self-reported measures of appetite in relation to verbal cues about many foods

In the present study a representative sample of students from a general college population were exposed to a list of written food cues and asked to rate each of the foods according to its nutritional value. Subjects who were exposed to the food list subsequently reported increases in hunger, desire to eat, and number of foods currently hungry for, as well as reduced fullness, compared to controls who were not exposed to the food list. Also, there was a trend for the food-cued subjects to report hunger for lower fat foods compared to the controls. The results are discussed in terms of previous research and suggestions for future research are provided.     

Generalized eta and omega squared statistics: measures of effect size for some common research designs

The editorial policies of several prominent educational and psychological journals require that researchers report some measure of effect size along with tests for statistical significance. In analysis of variance contexts, this requirement might be met by using eta squared or omega squared statistics. Current procedures for computing these measures of effect often do not consider the effect that design features of the study have on the size of these statistics. Because research-design features can have a large effect on the estimated proportion of explained variance, the use of partial eta or omega squared can be misleading. The present article provides formulas for computing generalized eta and omega squared statistics, which provide estimates of effect size that are comparable across a variety of research designs.     

Iconic memory and its relation to perceptual processing and other memory mechanisms

Research on iconic memory is reviewed. Specific issues discussed include the duration of the icon, effects of stimulus variables, types of information lost, selection, processing capacity, and scanning. More general issues include the level of encoding in the icon and its relation to short-term memory. It is also argued that a number of experiments do not show what they were intended to show because of possible methodological problems. The view is developed that iconic memory is postretinal but uncoded; nor is it influenced directly by strategies or subsequent mechanisms.     

Barrier and penetration scores in relation to some objective and subjective somesthetic measures

Barrier and Penetration scores in relation to some variables, such as muscular tone at rest, sensitivity to tickle, and body perception were studied in a group of 35 female subjects. While no correlations appear within the whole group of subjects between Barrier scores and the other variables, on the left side of the body. Dividing subjects on the basis of Barrier scores, three groups with different characteristics appear: 12 subjects with high Barrier scores show an inverse relation of Barrier scores with sensitivity to tickle on the right side of the body; 12 subjects with middle Barrier scores show a direct relation of Barrier scores with muscular tone and an inverse one with both latency of tickle on the right half of the body and body perception; 11 subjects with low Barrier scores show an inverse relation of Barrier scores with durations of tickle on both sides of the body.