Chi Square Test, McNemar Test

Question 1

A Chi Square Test is…

Answer 1

used to compare two or more independent groups for their proportions

a statistical hypothesis test that uses a test statistic with a known probability distribution of chi-square distribution

Question 2

How can you test statistically the effect of a new medication over the standard treatment on hypertensive subjects?

Answer 2

Run a statistical hypothesis test to compare the proportions of those who were responsive between experimental vs control groups.

Question 3

Degree of Freedom

Answer 3

number of values that are free to vary as you estimate parameters

Question 4

OR =

Answer 4

(a/b)/(c/d)

Question 5

RR =

Answer 5

[a/(a+b)] / [c/(c/d)]

Question 6

Assumptions for valid chi square tests

Answer 6

groups are independent

the value of the cell expected count should be 5 or more in at least 80% of cells

no cell should have an expected count less than 1

Question 7

McNemar test

Answer 7

form of chi square test used with 2x2 contingency table that involved matched samples, where subjects act as their own controls

Question 8

Fisher’s Exact test

Answer 8

statistical hypothesis test used when you want to compare proportions between the 2 independent groups when data are sparse

a test resulting in the exact probability of the occurence of observed frequencies, given marginal totals