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What is the item difficulty index(p)?

indicates the percent of examinees in the sample who answerede the item correctly
most situations a p=.50 is optimal except true/false tests where optimal p=.75 the closer that p=.50, the more differentiating the index is 

What is item discrimination?

extent to which a test item discriminates between examinees who obtain high versus low scores on a test


What is the basis of classical test theory?

views an obtained test score as reflecting a combination of truth and error


What is the problem with classical test theory?

items are dependent upon original sample
inability to compare scores obtained on different tests 

What is the basis of item response theory?

involves the use of an item characteristic curve that provides information on relationships between examinee's level on a trait measured by the test and the probability that he will respond correctly to the item


What are the 3 advantages of item response theory?

sample invariant
possible to equate test scores easier to develop computeradapted tests 

According to classical test theory, what are the components of an examinee's obtained test score?

and true score (T) plus and error component (E)
obtained score (X) = Truth + Error 

What does the error component represent in classical test theory?

represents measurement error which is due to factors that are irrelevant to what is being measured and have an unsystematic effect on the score


What is normreferenced interpretation?

transform raw scores into a normreferenced score (percentile rank, zscore, T score)


What is criterion referenced interpretation?

score interpreted in termso f total amount of test mastered (% correct) or in terms of some external criterion


What is reliability?

extent to which test performance is immune to the effects of measurement error


What is a reliability coefficient?

indicates whether the attribute measured by the test is being assessed in a consistent, precise way


How do you interpret a reliability coefficient?

the proportion of variability in obtained test scores that reflects true score variability
reliability coefficient is never squared r(xx)=true score variablity 1r(xx)=error 

What are the different forms of reliability?

testretest (coefficient of stability)
alternate forms (coefficient of equivalence) splithalf (coefficient of internal consistency) coefficient alpha (coefficient of internal consistency) interrater reliability (coefficient of concordance) 

What type of reliability is appropriate to measure time sampling error?

testretest (coefficient of stability)
measure attributes that are relatively stable over time 

What type of reliability is appropriate to measure time sampling and content sampling errors?

alternate forms (coefficient of equivalence)
not appropriate when attribute measured is expected to fluctuate over time most rigorous and best method for estimating reliability 

Why is alternate forms reliability often not assessed?

difficulty in developing forms that are truly equivalent


what are 2 methods for evaluating internal consistency?

splithalf
coefficient alpha 

What is the problem with using splithalf reliability?

reliability coefficient based on test scores from onehalf of entire test
reliability tends to decrease as the length of test decreasessplit half usually underestimates test's true reliability 

How can you correct for the problems with splithalf reliability?

use the SpearmanBrown prophecy formulaprovides an estimate of what the reliability coefficient would have been if it had been based on the full length of the test


When do you use the KuderRichardson Formula 20 (KR20)?

when test items are measured dichotomously
variation of coefficient alpha not appropriate for speeded tests 

What is a drawback of using coefficient alpha?

lower boundary of a test's reliability


What is the purpose of using coefficient alpha?

measure interitem consistency


When is it appropriate to use interrater reliability?

whenever test scores depend on a rater's judgement


When is a kappa coefficient used?

the reliablity coefficient for interrater reliabliity


What are the factors that affect the reliability coefficient?

test length
range of test scores guessing 

What is the acceptable level of a reliability coefficient?

.80 or larger


What is the standard error of measurement?

an index of the amount of error that can be expected in obtained scores due to the unreliability of the test
calculation of the confidence interval 

What is the formula for the standard error of measurement?

square root of 1r(xx) (reliability coefficient) multipled by the standard deviation of test scores


What affects the magnitude of the standard error?

standard deviation of test scores and test's reliability coefficient
lower the test's standard deviation and higher reliability coefficient = smaller standard error of measurement 

How can you interpret the standard error of measurement?

type of standard deviation
interpret in terms of areas under the normal curve 68%, 95%, 99% confidence intervals 1, 2, 3 standard deviations 

What is validity?

test's accuracy in providing information it was designed to provide


What are the 3 categories of validity?

content validity
construct validity criterionrelated validity 

What type of validity is important when scores on a test provide information on how much each examinee knows about a domain?

content and construct validity


What type of validity is important when scores on a test provide information on each examinee's status with regard to the trait being measured?

content and construct validity


What type of validity is important when scores will be used to predict scores on some other measure and you are interested in the predicted scores?

criterionrelated validity


What is content validity?

test items sample content or behavior test was designed to measure


How do you establish content validity?

through the judgement of experts


What type of tests consider content validity to be important?

achievementtype tests
work samples 

What additional evidence supports good content validity?

large coefficient of internal consistency
high correlations with other tests that measure the same domain pre/post test evaluations with a program designed to increase familiarity with material will show changes 

What is construct validity?

the test is found to measure theoretical trait or construct designed to measure


What are some methods to establish construct validity?

assess internal consistency
study group differences (adequate?) hypotheseis testingdo the scores change following the experiment assess convergent (high correlations with the same trait) and divergent (low correlations with different traits) validity assess factoral validity 

What are monotraitmonomethod coefficients?

same traitsame method
correlation between measure and itself reliability coefficients should be large 

What are monotraitheteromethod coefficients?

same traitdifferent method
correlation between different measures of the same trait convergent validity 

What are heterotraitmonomethod coefficients?

different traitsame method
correlations between different traits measured by the same method discriminant (divergent) validity 

What are heterotraitheteromethod coefficients?

different traitdifferent method
correlation between different traits measured by different methods discriminant validity when small 

What do factor loadings in factor analysis measure?

square it to determine the amount of variability in test scores explained by the factor


What is communality in factor analysis?

common variance
amount of variability in test scores that is due to the factors that the test shares in common to some degree with the other tests included in the analysis 

From the perspective of factor analysis, what are the components of a test's reliability?

communality
specificity error 

What is the relationship between reliability and communality?

communality is a lowerlimit estimate of a test's reliability coefficient


What are the two types of rotation of a factor matrix?

orthogonal
oblique 

What type of rotation has uncorrelated factors?

orthogonal


What type of rotation has correlated factors?

oblique
attributes measured by the factor are not independent 

When can you calculate a factor's communality from the factor loadings?

when factors are orthogonal
communality is equal to the sum of the squared factor loadings 

What is a measure of shared variability?

squared factor loading


What is criterionrelated validity?

strong correlation between test and a criterion


How is criterionrelated validity assessed?

correlating the scores of a sample of individualson the predictor with their scores on the criterion


What are the 2 types of criterionrelated validity?

concurrent & predicitive validity


What is the difference between concurrent and predictive validity?

the time when the predictor and the criterion are administered
predict future status vs. estimating current status 

What is an acceptable level for a validity coefficient?

.20 or .30
rarely exceed .60 

How do you interpret validity coefficient?

since correlation between 2 measuressquare the coefficient and interpret in terms of shared variability


How do you provide a measure of shared variability?

square the correlation between 2 measures (tests or variables)
how much variability in Y is explained by X 

What is the standard error of estimate?

used to construct a confidence interval around a predicted criterion score


What is the formula for standard error of estimate?

square root of 1validity coefficient squared multiplied by standard error of the estimate


When does the standard error of estimate = 0?

when the validity coefficient is equal to +/1


What is incremental validity?

the increase in correct decisions that can be expected if the predictor is used as a decisionmaking tool
involves using a scatterplot 

In a scatterplot of criterion and predictor scores, if the goal is to maximize the proportion of true positives, how do you do this?

set a high predictor cutoff scorewill reduce the number of false positives


What is the formula for incremental validity?

positive hit rate  base rate


What is the base rate?

proportion of people selected without the use of the predictor
dividing successful people (true positive + false negatives) by the total number of people 

What is the positive hit rate?

proportion of people who would have been selected on the basis of their predictor scores and who are successful on the criterion
true positives/ total positives 

What determines if a person is positive or negative?

predictor


What determines if a person is true or false?

criterion


What is the correction of attenuation formula used for?

to estimate what a predictor's validity coefficient would be if the predictor and/or criterion were perfectly reliable
tends to overestimate the actual validity coefficient that can be achieved 

What information is needed to calculate the correction of attenuation formula?

predictor's current reliability coefficient
criterion's current reliability coefficient criterionrelated validity coefficient 

What happens to the validity coefficient when it is crossvalidated?

tends to shrink because all of the same chance factors operating in the original sample will not ve present in the new sample


What is normreferenced interpretation?

comparing an examinee's test score to scores obtained by people included in a normative (standardization) sample
helps identify individual differences percentile ranks, standard scores, age and grade equivalent scores 

What is a nonlinear transformation?

whenever a distribution of transformed scores differs in shape from the distribution of raw scoresthe score transformation is this
percentile ranksbecause always flat in shape 

What is a standard score?

indicates the examinee's position in the normative sample in terms of standard deviations from the mean
permit comparisons of scores from different tests zscores Tscores, deviation IQs, and SAT scores 

What is the formula for calculating a zscore?

raw score  mean of distribution
divided by the distribution's standard deviation 

What is a linear transformation?

transformation of raw scores to zscores


What is the purpose of criterionreferenced (mastery) testing?

to make sure that all examinees eventually reach the same performance level


What is a type of criterionreferenced testing?

percentage score
or interpreting test scores in terms of their likely status on an external criterion 

When do you use a regression equation and expectancy tape when interpreting test scores?

criterionreferenced interpretation


What is banding?

score adjustment method involves considering people within a specific score range (band) as having identical scores


What is exploratory factor analysis?

identify the minimum number of underlying "factors" (dimensions) needed to explain the intercorrelations among a set of tests, subtests, or test items


What is principal components analysis?

used to identify a set of variablesthat explains all (or nearly all) of the total variance in a set of test scores


What eigenvalue is ued to retain components in a principal components analysis?

1.0 or higher
