In: Math
In 2001, a reproductive clinic reported 43 live births to 169 women under the age of 38, but only 9 live births for 75 clients aged 38 and older. Is there evidence of a difference in the effectiveness of the clinic's methods for older women? Determine the test statistic, the p-value, and if there is a difference, estimate the difference p1-p2 with a 95% confidence interval.
SOLUTION:
From given data,
In 2001, a reproductive clinic reported 43 live births to 169 women under the age of 38, but only 9 live births for 75 clients aged 38 and older. Is there evidence of a difference in the effectiveness of the clinic's methods for older women? Determine the test statistic, the p-value, and if there is a difference, estimate the difference p1-p2 with a 95% confidence interval.
= 43/169 = 0.254
n1 = 169
= 9/75 = 0.12
n2 = 75
= (n1 * + n2 * )/(n1 + n2)
= (169 * 0.254 + 75 * 0.12 )/(169 +75)
= 51.926 / 244
= 0.21281
q = 1- = 1- 0.21281 = 0.78719
SE = sqrt(p * q (1/n1 + 1/n2) )
SE = sqrt(0.21281 * 0.78719 (1/169 + 1/75) )
SE = 0.056788
Determine the test statistic
the test statistic = Z = ( - ) / SE
Z = (0.254 - 0.12) / 0.056788
Z = 2.35
Determine the p-value
For two tailed test,
P(|Z| > 2.35) = area on left of -2.35 and on right of 2.35
P(|Z| > 2.35) = 2* P(Z < - 2.35)
P(|Z| > 2.35) = 2* 0.00939
P(|Z| > 2.35) = 0.01878
Estimate the difference p1-p2 with a 95% confidence interval.
95% confidence interval
Confidence interval is 95%
95% = 95/100 = 0.95
= 1 - Confidence interval = 1-0.95 = 0.05
/2 = 0.05 / 2
= 0.025
Z/2 = Z0.025 = 1.96
Confidence interval :
( - ) Z/2 * SE
(0.254 - 0.12) 1.96 * 0.056788
0.134 0.11130448
(0.134 - 0.11130448 , 0.134 + 0.11130448)
(0.0226 , 0.2453)
0.0226 < p1-p2 < 0.2453