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Flashcards in Chi squared test Deck (6)
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1

What does the Chi squared test check for

association between 2 categorical variables. Calculates the frequencies that would be expected if no association->compares observed frequencies with expected values->if observed frequencies are very different=association

2

how to calculate the degrees of freedom for chi squared

(no. of rows-1)x(no. of columns-1)

3

Should you use frequency or % for chi squared test

frequency

4

Which estimates to use for 2x2 table in chi squared test

risk difference: p1-p2, use if actual size of difference is of interest
relative risk: p1/p2, use if relative difference is of interest, easier to interpret than OR but do not use for case control studies
Odds ratio: (p/(1-p))//(p2/(1-p2)) use for case control studies, approximately equal to relative risk when outcome is rare.Can be misinterpreted when outcome more common

5

Null hypothesis for chi squared

In the population where the samples come, there is no association between the 2 variables

6

Assumption of chi squared

large sample test, at least 80% of expected frequencies must be greater than 5. For 2x2 test, all frequencies>5