Question

A grocery​ store's receipts show that sunday customer purchases have a skewed distribution with a mean of ​$3030 and a standard deviation of ​$2121. suppose the store had 304304 customers this sunday. ​a) estimate the probability that the​ store's revenues were at least ​$9 comma 6009,600. ​b) if, on a typical​ sunday, the store serves 304304 ​customers, how much does the store take in on the worst 11​% of such​ days?

Answer 1

A. we use the z statistic to solve this problem

z = (x – u) / s

We calculate the value of the sample mean u and standard deviation s:

u = $30 * 304 = $9120

s = $21 * 304 = $6384

 

z = (9,600 – 9120) / 6384

z = 0.075

 

From the normal tables using right tailed test,

P = 0.47

 

B. At worst 11% means P = 0.11, so the z value at this is z = -1.23

-1.23 = (x – 9120) / 6384

x = 1267.68