Joel C.

a sample of examinees who are representative of the population for whom the test is intended

norm group

the most basic level of information provided by a psychological test, for example, the number of questions answered correctly

raw score

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a method of summarizing data or test scores by specifying a small number of usually equal-sized class intervals and then tallying how many scores fall within each interval

frequency distribution

a method of summarizing data or test scores in graphic form; a histogram contains the same information as a frequency distribution

histogram

a method of summarizing data or test scores in graphic form; similar to a histogram, except that the frequency of the class intervals is represented by single points rather than columns

frequency polygon

the arithmetic average of a group of scores

mean

the middlemost score when all the scores in a sample have been ranked

median

the most frequently occuring score

mode

a statistical index that reflects the degree of dispersion in a group of scores; the square root of the variance

standard deviation

a statistical index that reflects the degree of dispersion in a group of scores

variance

a symmetrical, mathematically defined, bell-shaped frequency distribution

normal distribution

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the symmetry or asymmetry of a frequency distibution; positive skew indicates that scores are piled up at the low end and negative skew indicates that scores are piled up at the high end

skewness

the percentage of persons in the standardization sample who scored below a specific raw score; percentiles vary from 0-100

percentile

a transformed score in which the original score is expressed as the distance from the mean in standard deviation units

standard score

a transformed score with mean of 50 and standard deviation of 10

T score

a score obtained by a transformation that renders a skewed distribution into a normal distribution

normalized standard score

a scale in which all raw scores are converted to a single-digit system of scores ranging from 1 - 9

stanine scale

a 10-unit scale with five units above and five units below the mean

sten scale

a variant on the stanine scale with 11 units

c scale

a selection strategy in which every subject has an equal chance of being chosen

random sampling

a selection strategy in which subjects are chosen randomly, with the constraint that the sample matches the population on relevant background variable such as race, sex, occupation, and so on

stratified random sampling

a type of standardization that depicts the level of test performance for each separate age group in the normative sample

age norm

a type of standardization that depicts the level of test performance for each separate school grade in the normative sample

grade norm

norm derived from a representative local sample, as opposed to a national sample

local norm

norms derived from an identified subgroup, as opposed to a diversified national sample

subgroup norms

a table that portrays the established relationship between test scores and expected outcome on a relevant task

expectancy table

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