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Flashcards in Chapter 5 Deck (7)
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1

Variability

a measure of the spread, or dispersion, of a set of data. Once the mean, median, and mode have been calculated, the central tendencies of the raw data are known.

2

Interquartile Range

a measure of variability used when data are ordinal, or when ratio or interval data are highly skewed; This range is the difference between the raw scores at the 75th (Q3) and the 25th (Q1) percentile points.
IQR = Q3−Q1

3

Semi-Interquartile Range

alternative measure of variability when using percentiles; which is half of the interquartile range. The formula is SIQR = (Q3−Q1)/2. This measure is used if a smaller indicator of the variability is desire

4

Variance

the average of the squared deviations from the mean. The symbol V is used for variance in this text; other texts may use the symbol S2; represented in algebraic terms
as follows: V =Σ(X−X)^2/N.

5

Sum of Squares

type of calculation where we add up squared values

6

Standard Deviation

the square root of the average of the squared deviations from the mean (i.e., it is the square root of the variance); applies to a population of scores

7

Degrees of Freedom

the number of values in a data set that are free to vary; is, they may take on any value, limited only by the precision of the measuring instrument and
the actual values in the population