Module 3: Statistical Reasoning in Everyday Life

Question 1

Mode

Answer 1

Most frequently occurring score(s) in a
distribution.

Question 2

Median

Answer 2

Middle score in a distribution; half the scores are above it, and half are below it.

Question 3

Mean

Answer 3

Arithmetic average of a distribution, obtained by adding the scores and then dividing by the number of scores; can be distorted by few atypical scores.

Question 4

Range

Answer 4

Difference between the highest and lowest
scores in a distribution.

Question 5

Standard Deviation

Answer 5

Computed measure of how much scores vary around the mean score.

Question 5

Normal Curve (Normal Distribution)

Answer 5

Symmetrical, bell-shaped curve that describes the distribution of many types of data; most scores fall near the mean
(about 68 percent fall within one standard deviation of it), and fewer and fewer occur near the extremes.

Question 6

When is an observed difference reliable? (three reasons)

Answer 6

(1) Representative samples are better than biased samples. (2) Less variable observations are more reliable than
more variable observations. (3) More cases are better than fewer.

Question 7

Statistical Significance

Answer 7

A statement of how likely it is that a result (such as a difference between samples) occurred by chance, assuming there is no difference between the populations being studied.

Question 8

When is an observed difference significant? (two reasons)

Answer 8

(1) When sample averages are reliable and the difference between them is relatively large, the difference has statistical significance. (2) Observed difference is probably not due to chance variation between the samples.

Question 9

What does proof beyond a reasonable doubt mean?

Answer 9

When the odds of an outcome’s
occurrence by chance are less than 5 percent.