Chapter 9 - Data on categorical variables

Question 1

Expected count in cell

Answer 1

Row (R) multiplied by the Column (C) divided by the overall total (n)

Question 2

Cell contribution

Answer 2

The contribution a cell makes to the Chi-square statistic

Question 3

Chi-square statistic

Answer 3

A measure of the difference between the observed counts and the expected counts if the null hypothesis was true. The sum of all cell contributions.

Question 4

Chi-square test

Answer 4

A hypothesis test based on the Chi-square distribution. An overall test to compare the observed counts and the expected counts in one or more categories.

Question 5

Expected count

Answer 5

The number of observations expected to be in a category if the null hypothesis was true.

Question 6

Observed count

Answer 6

The number of observations in a cell in a two-way table

Question 7

Statistical inference

Answer 7

Going beyond the data at hand, either by generalising the observed results to a larger group or population (sample-to-population inference) or by drawing a more profound conclusion about the type of relationship between two variables such as, in an experiment, the explanatory variable causes a change in the response.

Question 8

Statistical significance

Answer 8

Relates to the size of the P-value: a difference is statistically significant if it has a small P-value, commonly less than 5%

Question 9

Statistically significant

Answer 9

An observed difference is so large that it cannot reasonably be attributed to chance alone.
An observed difference is unlikely to have happened by chance alone.