Question

Hoping to lure more shoppers​ downtown, a city builds a new public parking garage in the central business district. The city plans to pay for the structure through parking fees. For a random sample of 44 ​weekdays, daily fees collected averaged ​$131​, with standard deviation of ​$13.

a) What assumptions must you make in order to use these statistics for​ inference?

Select all that apply.

​b) Find a 90​% confidence interval for the mean daily income this parking garage will generate.

The 90​% confidence interval for the mean daily income is ___ , ___ (Round two decimal places)

Answer 1

Here average daily fees collected = = $ 131

Standard deviation = s = $ 13

Sample size = n = 44

(a) Here options for assumptions are not given. But in order to use these statistic for inference we should know that the sampling is simple random sampling. All samples are independent of each other

(b) Here standard error = s/sqrt(n) = 13/sqrt(44) = 1.96

90% confidence interval = +- t_critical se

Degree of freedom = dF = 44 -1 = 43

Critical value = t_critical = TINV(0.10, 43) = 1.681

90% confidence interval = 131 +- 1.681 * 1.96 = ($127.71, $134.29)