In: Statistics and Probability
We would like to know: "What percentage of college students drink alcohol every day?" In a random sample of 500 students, 75 said they drink alcohol every day. Use the data to construct a 95% confidence interval to answer to the question. You MUST show your work to receive full credit.
Solution :
Given that,
n = 500
x = 75
Point estimate = sample proportion = = x / n = 0.15
1 - = 0.85
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
Margin of error = E = Z / 2 * (( * (1 - )) / n)
= 1.96 * (((0.15 * 0.85) / 500)
= 0.031
A 95% confidence interval for population proportion p is ,
- E < p < + E
0.15 - 0.031 < p < 0.15 + 0.031
0.119 < p < 0.181
( 0.119 , 0.181 )