Answer:
0.02683<x<0.133173
Explanation:
The confidence interval formula is expressed as;
CI = p ± z√p(1-p)/n
p is the proportion
z is the confidence interval at 95% confidence
n is the sample size
Since it is found that a sample of size 100 yields 8 defectives, the sample proportion p = 8/100 = 0.08
Given
n = 100
z score = 1.96
p = 0.08
1-p = 1-0.08 = 0.92
Required
95% confidence interval
Substitute the given parameters into the formula as shown;
CI = p ± z√p(1-p)/n
CI = 0.08 ± 1.96√0.08(0.92)/100
CI = 0.08 ± 1.96√0.0736/100
CI = 0.08 ± 1.96(0.027129)
CI = 0.08 ± 0.053173
CI = (0.08-0.053173, 0.08+0.053173)
CI = (0.02683, 0.133173)
Hence the 95% confidence intervals for the proportion of defective items is 0.02683<x<0.133173