Describing Data with Numbers: Central Tendency and Variability Key Terms

Question 1

Central Tendency

Answer 1

Typical or most representative value of a group of scores.

Question 2

Deviation

Answer 2

The difference between a value in the data set and the mean of the data set.

Question 3

Empirical Rule

Answer 3

Rule states that for data sets having a distribution that is approximately bell-shaped, the following properties apply:  About 68% of all values fall within one standard deviation of the mean.  About 95% of all values fall within two standard deviations of the mean.  About 99.7% of all values fall within three standard deviations of the mean.

Question 4

Mean

Answer 4

The sum of all values divided by the total number of values. It is what is most commonly called the arithmetic average.

Question 5

Median

Answer 5

The middle score when all the scores in a distribution are arranged from lowest to highest (or halfway between the two middle values if the number of values is even).

Question 6

Mode

Answer 6

The value with the greatest frequency in a distribution.

Question 7

Outlier

Answer 7

Score with an extreme value (very high or very low) in relation to the other scores in the distribution.

Question 8

Percentiles

Answer 8

Measures of location, which divide a set of data into 100 groups with about 1% of the values in each group.

Question 9

Range

Answer 9

The difference between the maximum and minimum data entries in the set.

Question 10

Range Rule of Thumb

Answer 10

A guideline stipulating that, for a data set with no outliers, the standard deviation is approximately equal to the range divided by 4.

Question 11

Standard Deviation

Answer 11

A measure of variation of scores about the mean. It is approximately the average amount that scores vary from the mean.

Question 12

Variance

Answer 12

Measure of how spread out a set of scores is; average of the squared deviations from the mean.