Complete question :
The manager of a bank recorded the amount of time each customer spent
waiting in line during peak business hours one Monday. The frequency distribution below summarizes the results. Find the standard deviation. Round your answer to one decimal place. 0-4 ,4-8,8-12,12-16,16-20,20-24 number 11,15,15,8,0,1
Answer:
4.517
Explanation:
Given the data:
______m __ f___fx __f(m - x)²
0-4 __ 2___11__22 __ 385.51
4-8 __ 6___15__90__ 55.29
8-12 _ 10__ 15__150__64.896
12-16_ 14___8__112__295.73
16-20_18__ 0__ 0 ___0
20-24_22__1__ 22 ___198.25
Mean (x) = Σfx / Σf
Mean = (22 + 90 + 150 + 112 + 0 + 22) / (11 + 15 + 15 + 8 + 0 + 1)
= 396 / 50
= 7.92
Standard deviation :
√(385.51 + 55.29 + 64.896 + 295.73 + 0 + 198.25) / 49
√20.40155102041
= 4.517