Chi Square

Question 1

What is the symbol for Chi Square?

Answer 1

χ2

Question 2

When do we use Chi Square test?

Answer 2

When we have nominal data :) e.g. categories like male, female.

Question 3

Chi square is usually used where we have __ variables, each of which are assessed on a _____ scale.

Answer 3

2

nominal

Question 4

Do we use Chi Square on:
repeated measures design
OR
independent groups design?

Answer 4

Independent Groups Design

Question 5

How do you report a Chi Square?

Answer 5

χ2 (df, n =….) = chi square, p = xxx

Question 6

If the Chi Square has a significant effect what do we report?

Answer 6

The sample size e.g. n = xxx.

Question 7

What does Chi Square Test?

Answer 7

The association between 2 nominal/categorical variables.

Question 8

What is the descriptive statistic for a Chi Square?

Answer 8

A contingency table

Question 9

How do you calculate the expected frequencies for each cell?

Answer 9

Multiply to row total by the column total.

Then divide by the number of participants.

Question 10

Why do you calculate expected values for each of the cells?

Answer 10

To compare these with our observed values.

Question 11

How is chi square calculated?

Answer 11

the sum of:
(o - e)2/ e

o = observed values
e = expected values

Question 12

Th chi square value will get ____ as the difference between the observed and expected values increases.

Answer 12

bigger

Question 13

What is the standard way to report Chi Square?

Answer 13

χ2 (df, n = 100) = pearson Chi square, p = .xxx (two-tailed) [plus effect size if significant].

Question 14

If the Chi Square is significant what do you need to do?

Answer 14

You need to explain what the association was using the observed and expected frequencies e.g. “more males (13) were smokers than we’d expect by chance (10)”

Question 15

What do we need to double check for in any Chi square?

Answer 15

Expected cell counts!

Need to be less than 20% of counts under 5.

Question 16

For chi square, you are only allowed to have fewer than ____ of your expected cell counts under 5.

Answer 16

20%

Question 17

What do you do if you have more than 20% of your expected counts under 5?

Answer 17

Report the Fisher’s Exact Test.

just report the p value

Question 18

What should you use for your chi square effect size? If you have a 2 x 2 table?

Answer 18

Phi Coefficient

Question 19

What effect size is used for more complex data?

Answer 19

Cramer’s v

Question 20

What does the phi coefficient range from?

Answer 20

0 to 1

Question 21

A value closer to 1 reflects what?

Answer 21

A larger effect!

Question 22

What is a small effect size?

Answer 22

.1 to .3

Question 23

What is a medium effect size?

Answer 23

.3-.5

Question 24

What is a large effect size?

Answer 24

over .5

Question 25

What are the 2 ways to deal with low expected cell counts (e.g. more than 20% under 5)

Answer 25

1. you can ignore a group

2. you can merge 2 groups together

Question 26

For G power:

What proportions do we have to set?

Answer 26

set proportion p 2
people in treatment group/outcome

set proportion p1
people in control group/outcome

Question 27

For G power:

how do we change the allocation ratio?

Answer 27

If there is 50 people in each group then fab it’s 1!

If not divide smallest group/ bigger group and get a number :)

Question 28

Chi square is a ____ test.

Answer 28

non-parametric