2 Proportion Z-Test

P1= 3/19
P2= 6/21

H0: P1 = P2
Ha: P1 ≠ P2

p = (p₁ * n₁ + p₂ * n₂) / (n₁ + n₂)
p = (3 + 6) / 40 = 0.225

Test for Independence

• Random Sample
• np=(40)(.225)=9
• nq=(40)(1-.225)=31

Because nq is greater than 10, the date is said to be independent and therefore a 2 proportion z-test can be applied.

SE = sqrt{ p * ( 1 - p ) * [ (1/n₁) + (1/n₂) ] }
SE = sqrt{0.225(1-0.225) [(1/19)+(1/21)] }
SE = 0.132

z = (p₁ - p₂) / SE
z = [(3/19) - (6/21)] / 0.132
z = -0.968

p value: .1660= 16.60%