In: Statistics and Probability
A survey indicated that 28% of tenured university professors are female. Suppose the survey was based on a sample of 500 professors.
The 95% confidence interval for the population proportion, p, is
Group of answer choices
0.26 to 0.30
0.24 to 0.32
0.27 to 0.29
0.28 to 0.34
Solution :
Given that,
n = 500
Point estimate = sample proportion = =0.28
1 - = 0.72
At 95% confidence level the z is ,
= 1 - 95% = 1 - 0.95 = 0.05
/ 2 = 0.05 / 2 = 0.025
Z/2 = Z0.025 = 1.96 ( Using z table )
Margin of error = E = Z/2 * ((( * (1 - )) / n)
= 1.96 (((0.28*0.72) /500 )
E = 0.04
A 95% confidence interval proportion p is ,
- E < p < + E
0.28-0.04 < p < 0.28 +0.04
0.24 to 0.32