In: Statistics and Probability
Construct a confidence Interval for p1- p2, at a 95% level of confidence, if x1= 366, n1=535, x2=435, n2=593
Solution :
Given that,
n1 = 535
x1 = 366
= x1 / n1 = 366 / 535 = 0.684
1 - = 1 - 0.684 = 0.316
At 95% confidence level the z is ,
= 1 - 95% = 1 - 0.95 = 0.05
/ 2 = 0.05 / 2 = 0.025
Z/2 = Z0.025 = 1.960
Margin of error = E = Z / 2 * (( * (1 - )) / n)
= 1.960 * (((0.684 * 0.316) / 535) = 0.039
A 90 % confidence interval for population proportion p1 is ,
- E < P1 < + E
0.684 - 0.039 < p < 0.684 + 0.039
0.645 < p < 0.723
The 95% confidence interval for the population proportion p1 is : ( 0.645 , 0.723)
Given that,
n2 = 593
x 2 = 435
= x / n = 435 / 593 =0.734
1 - = 1 - 0734. = 0.266
At 95% confidence level the z is ,
= 1 - 95% = 1 - 0.95 = 0.05
/ 2 = 0.05 / 2 = 0.025
Z/2 = Z0.025 = 1.960
Margin of error = E = Z / 2 * (( * (1 - )) / n)
= 1.960 * (((0.734 * 0.266) / 593) = 0.036
A 95 % confidence interval for population proportion p2 is ,
- E < P2 < + E
0.734 - 0.036 < p < 0.734 + 0.036
0.698 < p2 < 0.770
The 95% confidence interval for the population proportion p2 is : ( 0.698 , 0.770)