A psychologist wishes to determine whether Tourette's syndrome occurs more in males than in females. She noted the gender and the absence and presence of Tourette's syndrome in a large hospital's consecutive admissions for the past 5 years. Are gender and Tourette's syndrome independent?
1024 men without Tourette's
27 men with Tourette's
986 women without Tourette's
9 women with Tourette's
This problem requires the computation of a chi-square test with a two-by-two design. The null and alternative hypotheses are as follows:
H0: pT-m = pT-f
Ha: pT-m ≠ pT-f
Where
pT-m = the probability of having Tourette's syndrome for males, and
pT-f = the probability of having Tourette's syndrome for females.