Chi-Square Test Goodness of Fit

Expected Counts for a Chi-Square Test for Goodness of Fit

npi

Chi-square test statistic

is a measure of how far the observed counts are from the expected counts, relative to the expected counts

X² = sum of (observed count - expected count)² / expected count

Chi-square distribution

defined by a density curve that takes only nonnegative values and is skewed to the right

Conditions for Chi-Square Goodness of Fit

• Random - data comes from a random sample

• 10% - when sampling without replacement n<10%N

• Large counts - All expected counts are at least