Chi-square And Goodness Of Fit

Question 1

Cross-table

Answer 1

• Rows and columns table (rows x column)
• degrees of freedom: (r - 1) (c - 1)

Question 2

Chi-square =

Answer 2

Z^2
- compare two groups using a z-test for two proportions or chi-square.

Question 3

Expected count

Answer 3

Expected count = row total x column total / n

Question 4

Null hypothesis

Answer 4

• Rows and columns are independent

Question 5

Goodness of fit

Answer 5

• comparing values against a single variable
• degrees of freedom = k - 1 (k = # of categories)
• expected count = n x pi

Question 6

Chi-square distributions

Answer 6

• always positive
• if EC and OC are too different = large X2 = reject H0.

Question 7

Chi-square for independence

Answer 7

• norminal
• p-value = test value >- critical value

Question 8

Assumption for chi-square test

Answer 8

1. All cells in the cross table have en expected value of 1 or higher
2. Percentage of cells with expected count lower than 5 should not be more than 20% of the total number of cells
3. All 4 expected counts in 2x2 table should be 5 or greaterr