Answer:
90% Confidence Interval = (5.532, 7.094)
Step-by-step explanation:
With a sample size of 14 cars, the average wait time is 6.313 minutes with a standard deviation of 1.6509 minutes. Construct a 90% confidence interval for the true average wait time for a car at the intersection between 4:00 PM and 5:00 PM. 1) (4.542, 8.084).2) (5.536, 7.09). 3) (-5.532, 7.094).4) (5.532, 7.094).5) (5.872, 6.754).
We are given the sample size = 14 cars
This sample size is small so instead of using z score , we would use the t score critical value
First we need to calculate our degree of freedom
Degrees of freedom = n - 1
= 14 - 1 = 13
The t score for 90% confidence interval with a degree of freedom of 13 =
= 1.771
Hence, Confidence Interval =
Mean ± t score × standard deviation/√n
= 6.313 ± 1.771 × 1.6509/√14
= 6.313 ± 1.771 × 0.4412215843
= 6.313 ± 0.7814034257
Confidence Interval
= 6.313 - 0.7814034257
= 5.5315965743
≈ 5.532
= 6.313 + 0.7814034257
= 7.0944034257
≈ 7.094
90% Confidence Interval = (5.532, 7.094)
