In: Statistics and Probability
As a condition of employment, Fashion Industries applicants must
pass a drug test. Of the last 210 applicants, 24 failed the
test.
(1) Develop a 90% confidence interval for the proportion of
applicants that fail the test. (Round your answers to 3 decimal
places.)
(2) Yes or no...Would it be reasonable to conclude that more than
7% of the applicants are now failing the test?
Solution :
Given that,
n = 210
x = 24
= x / n =24 /210 = 0.114
1 - = 1 - 0.114 = 0.886
At 90% confidence level the z is ,
= 1 - 90% = 1 - 0.90 = 0.10
/ 2 = 0.10 / 2 = 0.05
Z/2 = Z0.05 = 1.645
Margin of error = E = Z / 2 * (( * (1 - )) / n)
= 1.645 * (((0.114 * 0.886) / 210) = 0.036
A 90 % confidence interval for population proportion p is ,
- E < P < + E
0.114 - 0.036 < p < 0.114 + 0.036
0.078 < p < 0.150
The 90% confidence interval for the population proportion p is : ( 0.078 , 0.150)
(2) yes