In a study that look into the association between age and headaches, a random sample of 811 people ages 30-39, 318 reported that they have a headache at least one night a week. In another random sample of 184 people ages 20-29, 48 reported that they have a headache at least one night a week.

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Output 1 Method P1: proportion where Sample 1 = Event P2: proportion where Sample 2 = Event Difference: P1 - P2 Descriptive Statistics Sample N Event Sample p Sample 1 811 318 0.392109 Sample 2 184 48 0.260870 Estimation for Difference Difference 95% Cl for Difference 0.131239 (0.059444, 0.203034) CI based on normal approximation Test Null hypothesis Ho: p1 - P2 = 0 Alternative hypothesis H,: p, - P2 # 0 Method Z-Value P-Value Normal approximation 3.33 0.001 Fisher's exact 0.001 The test based on the normal approximation uses the pooled estimate of the proportion (0.367839).Output 2 Method p: event proportion Normal approximation method is used for this analysis. Descriptive Statistics N Event Sample p 95% Cl for p 995 366 0.367839 (0.337877, 0.397802) Test Null hypothesis Ho: p = 0.5 Alternative hypothesis H,: p # 0.5 Z-Value P-Value -8.34 0.000