Categorical data Flashcards
1
Q
what is abo blood group an example of
A
nominal variable
2
Q
what is tumour stage an example of
A
ordinal variable
3
Q
what is a catergorical varibale taht has two levels called
A
binary variable
4
Q
what does chisqaured do
A
It compares observed results to expected
5
Q
what are importanyt things about the chi squared test
A
- make sure it is counts in cells not proportions
- make sure each independasnt unit appears once on the table
-make sure the expected values are not too small
6
Q
what would you use when the expected i smaller thsan 5 casts
A
fisher exact test
7
Q
why is the fishers exact test not always used
A
- too many tables when the counts are large
- no need chi sqaured is usually adequate
- exact test doesnt need approxiamtion but corresponsing confidence intervals are often too wide
8
Q
what are the 3 ways of finding a difference between parameters pi1 and pi2
A
- the abosultue difference
-the relative risk
-the odds ratio
9
Q
when would you not use an agreement statitsic
A
- when comparing measurements taken in differnet subjevcts
- when there has been an intervention that is likely to have affected the measured trait
- measurements are likely to be different
- hypothesis testing
-to find evidence taht a differnce does exist
10
Q
what test allows inter rate agreement
A
kohens kappa
11
Q
what are the 3 steps of chisquared
A
- make a table of what you would expect
find how. far from obserevd - work out how suprosiing the difference is
