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?
Accepted Solution
A:
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