Page 32 - Quantitative Data Analysis

Quantitative Data Analysis
Simply Explained Using SPSS

Measures of Dispersion

A measure of dispersion (variability) is also a descriptive statistic
that refers to how closely the data cluster around (or how spread
out around) some measure of central tendency.
1. Range

Range is the difference between the highest and lowest values

Formula: Range = maximum - minimum

2. Percentile

a. The k percentile is the value such that k% of the
th
ordered data falls at or below the value.

b. Location:

th
c. Note: L is the location of the k percentile, not the
value of the percentile.

3. Quartile

a. The quartiles divide the ordered data into four
equal groupings.

b. Each quartile (Q 1 , Q 2, and Q 3) marks the 25%, 50%,
and 75% percentiles of the data, respectively.

The Theory and Applications of Statistical Inferences 16