In: Statistics and Probability
Kate’s survey showed that 54 of 120 employees eat fast food at least once a week for lunch. What is the proportion of employees who eat fast food at least once a week, using a 98% confidence interval?
Group of answer choices
24% to 44%
30% to 50%
34% to 56%
28% to 45%
Solution :
Given that,
Point estimate = sample proportion = = x / n = 54/120=0.45
1 - = 1-0.45 =0.55
At 98% confidence level the z is ,
= 1 - 98% = 1 - 0.98 = 0.02
/ 2 = 0.02/ 2 = 0.01
Z/2 = Z0.01 = 2.326 ( Using z table )
Margin of error = E = Z/2 *( (( * (1 - )) / n)
= 2.326 (((0.45*0.55) /120 )
E = 0.11
A 98% confidence interval for population proportion p is ,
- E < p < + E
0.45-0.11 < p < 0.45+0.11
0.34< p < 0.56
34% to 56%