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okep
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Homework Statement
The time in minutes (min.) it takes Jessica to bicycle to school is normally distributed with mean 15 and variance 4. Jessica has to be at school at 8:00 am. What time shoud she leave her house so she will be late only 4% of the time?
A. 8:00 B) 11.5 min. before 8:00 C) 22 min. before 8:00 D) 18.5 min. before 8:00.
Answer: D) 18.5 min. before 8:00.
Homework Equations
Z = 1.96 for 95% CI
phat = 0.04; qhat = 0.96
+/- Z[phat*qhat/sqrt(n)]
15 +/- Z[phat*qhat/sqrt(n)]
The Attempt at a Solution
15 +/- Z[phat*qhat/sqrt(n)]
15 +/- 1.96[0.04*0.96/sqrt(60)]
= 0.025 min <--incorrect
The answer should be D) 18.5 min. But where did i go wrong? How do i solve this problem? Thanks.