Dollars Spent		Part a			Formula
11		Mean	41.31		=AVERAGE(A:A)
69
25		Part b
66		Standard Deviation	23.23		=STDEV.S(A:A)
30
37		Part c
33		Degrees of Freedom	15		=COUNT(A:A)-1
43
53		Lower Limit Critical Chi-square	18.2451		=CHISQ.INV.RT(0.25,D8)
19		Upper Limit Critical Chi-square	6.2621		=CHISQ.INV.RT(0.975,D8)
13
97		The 95% confidence interval
43		C.I.Lower Limit	21.06		=SQRT(D8*D5^2/D10)
33		C.I.Upper Limit	35.95		=SQRT(D8*D5^2/D11)
63
26

Americans spend nearly $7 billion on Halloween costumes and decorations. Sample data showing the amount, in dollars, 16 adults spent on a Halloween costume are contained in the Excel Online file below. Construct a spreadsheet to answer the following questions.

a. What is the point estimate of the population mean amount adults spend on a Halloween costume (to 2 decimals)? $41.31

b. What is the sample standard deviation (to 2 decimals)? $23.23

c. Provide a 95% confidence interval estimate of the population standard deviation for the amount adults spend on a Halloween costume (to 2 decimals)?

$21.06 $35.95

It is telling me that $21.06 in the 95% confidence is wrong. Can you help me figure out what I did wrong?