analysing categorical data Flashcards
(17 cards)
what table do we create to analyse categorical data?
contingency
what test do we perform on categorical data?
chi square test
what is a contingency table?
a table of frequencies for how often an observation occurs in a category
what are the 2 requirements for the categories in the contingency table?
mutually exclusive and exhaustive
what does the chi square test calculate?
how often a particular observation falls into a category based on how many were expected by chance
what is the null hypothesis?
frequencies observed were expected by chance
what is the alternative hypothesis?
frequencies observed reflect real differences in categories
what is independence in the chi square assumptions?
each person can only contribute to one cell of a contingency table
what is expected frequencies in the chi square assumptions?
all expected counts should be greater than 1 and no more than 20% of expected counts should be less than 5 so if violated power is reduced
what is the options if expected frequencies has been violated?
use an exact test
collapse data across one variable
collapse levels of one variable
collect more data
accept the loss of power
what is the chi square formula?
expected value
what are the 3 steps to calculate chi squared
- calculate expected frequencies
- calculate chi square value based on observed and expected
- compare chi square value against critical
what happens in chi squared if there’s two IV?
difference will be in calculating the expected values in each case
in spss what is the steps for 1 IV?
analyse
non parametric
legacy dialog
chi square
chi square SPSS steps for 2 IVS?
analyse
descriptive
cross tabs
how to get binomial on spss?
analyse
non parametric
legacy dialogs
binomial
what is a binomial test?
compare observed and expected frequencies for variables with only two levels
