Answer:
90% confidence interval for the mean commute time of working adult Calgary residents is between a lower limit of 26.72 minutes and an upper limit of 30.28 minutes.
Step-by-step explanation:
Confidence Interval = Mean + or - Error margin (E)
mean = 28.5 minutes
sd = 24.2 minutes
n = 500
degree of freedom = n - 1 = 500 - 1 = 499
confidence level = 90%
t-value corresponding to 499 degrees of freedom and 90% confidence level = 1.64801
E = t × sd/√n = 1.64801 × 24.2/√500 = 1.78
Lower limit = mean - E = 28.5 - 1.78 = 26.72 minutes
Upper limit = mean + E = 28.5 + 1.78 = 30.28 minutes
90% confidence interval is between 26.72 and 30.28 minutes.
