Chapter 5

Question 1

Variability

Answer 1

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.

Question 2

Interquartile Range

Answer 2

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

Question 3

Semi-Interquartile Range

Answer 3

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

Question 4

Variance

Answer 4

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.

Question 5

Sum of Squares

Answer 5

type of calculation where we add up squared values

Question 6

Standard Deviation

Answer 6

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

Question 7

Degrees of Freedom

Answer 7

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