PSY598 CHAPTER 3 SHUM TEST SCORES AND NORMS

What are norms?

Tables of the distribution of scores on a test for specified groups in a population that allow interpretation of any individuals score on the test compared to scores for a relevant group.

Item score

Score for each item on a test.

Raw score total

(raw score) total score on test found by adding item scores.

criterion referencing

A way of giving meaning to a test score by specifying the standard that needs to be reached in relation to a limited set of behaviours.

Norm referencing

A way of giving meaning to a test score relating it to performance of an appropriate reference group for that person.

Linear transformation

A transformation that keeps the order and equivalence of distance of the original set of scores.

Nonlinear transformation

A transformation that preserves the order but not the equivalence of distance of the original scores.

In geometry, a straight line uses what useful equation to translate test scores?

Y = mX + c

Explain Y = mX + c

Y is equal to a weighting factor which is m,

multiplied by the raw score which is X, plus a

constant (c)

z score

a linear transformation of test scores that express the distance of each score from the mean of the distribution of scores in units of the standard deviation of the distribution.

percentile

an expression of the position of a score in a distribution of scores by dividing the distribution into 100 equal parts; also known as 'centile'

normal curve

a bell shaped distribution of scores that conforms to a particular mathematical function that is a good approximation for random variables that cluster around a single mean.

standard score

the distance of a score in a normal distribution from mean expressed as a ratio of the standard deviation of the distribution.

Deviation IQ

A method that allows an individuals score to be compared with same-age peers; the score is reported as distance from the mean in standard deviation units.

Standardised Score

A score based on a z score, but set to a distribution with a particular mean and standard deviation considered convenient for a particular purpose.

T-score

A score standardised to a distribution with a mean of 50 and a standard deviation of 10.

Sten Scores

A point on a scale that has 5 units above mean and 5 units below mean. Scores ranges from 1 to 10. Mean of 5.5 with a standard deviation of 2.

Normalised standard score

A score in a distribution that has been altered to conform to a normal distribution by calculating the z scores for each percentile equivalent of the original raw score distribution.

Stanine

score on a 9 point scale with the points set in terms of percentiles.

Rasch model

Model that relates the probability of response at a particular sort (e.g. right/wrong) to the difference between a person's standing on a latent variable and the difficulty of the item.

Legit Scale

An equal interval scale that locates the person's standing on the underlying trait of interest in terms of the percentage of the items they get correct on the test and the average difficulty level of the items.

Ordinal Scale

A scale that has the property of a nominal scale, but also identifies on ordering of the objects in terms of the attribute.

Expectancy Table

A table that presents the probability of an outcome on a criterion of interest in terms of score on score range on a test.

Local norms

Norms developed for specific population groups or geographical regions.

Random Sampling

a sample that fairly represents a population because each member has an equal chance of inclusion - a selection of one member does not affect in any way the selection of any other member.

Stratified Sampling

process that allows a researcher to ensure that the sample represents the population on some characteristics that are considered important for the purpose of the study.