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EPPP Test Construction


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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 computer-adapted 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 norm-referenced 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 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
What are the different forms of reliability?
test-retest (coefficient of stability)
alternate forms (coefficient of equivalence)
split-half (coefficient of internal consistency)
coefficient alpha (coefficient of internal consistency)
inter-rater reliability (coefficient of concordance)
What type of reliability is appropriate to measure time sampling error?
test-retest (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?
coefficient alpha
What is the problem with using split-half reliability?
reliability coefficient based on test scores from one-half of entire test

reliability tends to decrease as the length of test decreases-split half usually underestimates test's true reliability
How can you correct for the problems with split-half reliability?
use the Spearman-Brown prophecy formula-provides 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 Kuder-Richardson Formula 20 (KR-20)?
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 inter-item consistency
When is it appropriate to use inter-rater reliability?
whenever test scores depend on a rater's judgement
When is a kappa coefficient used?
the reliablity coefficient for inter-rater reliabliity
What are the factors that affect the reliability coefficient?
test length
range of test scores
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 1-r(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
criterion-related 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?
criterion-related 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?
achievement-type 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 testing-do 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 monotrait-monomethod coefficients?
same trait-same method
correlation between measure and itself
reliability coefficients
should be large
What are monotrait-heteromethod coefficients?
same trait-different method
correlation between different measures of the same trait
convergent validity
What are heterotrait-monomethod coefficients?
different trait-same method
correlations between different traits measured by the same method
discriminant (divergent) validity
What are heterotrait-heteromethod coefficients?
different trait-different 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?
What is the relationship between reliability and communality?
communality is a lower-limit estimate of a test's reliability coefficient
What are the two types of rotation of a factor matrix?
What type of rotation has uncorrelated factors?
What type of rotation has correlated factors?
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 criterion-related validity?
strong correlation between test and a criterion
How is criterion-related validity assessed?
correlating the scores of a sample of individualson the predictor with their scores on the criterion
What are the 2 types of criterion-related 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 measures-square 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 1-validity 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 decision-making 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 score-will 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?
What determines if a person is true or false?
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
criterion-related validity coefficient
What happens to the validity coefficient when it is cross-validated?
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 a nonlinear transformation?
whenever a distribution of transformed scores differs in shape from the distribution of raw scores-the score transformation is this
percentile ranks-because 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
T-scores, deviation IQs, and SAT scores
What is the formula for calculating a z-score?
raw score - mean of distribution
divided by the distribution's standard deviation
What is a linear transformation?
transformation of raw scores to z-scores
What is the purpose of criterion-referenced (mastery) testing?
to make sure that all examinees eventually reach the same performance level
What is a type of criterion-referenced 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?
criterion-referenced 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

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