Question

Six different national brands of chocolate chip cookies were randomly selected at the supermarket. The grams of fat per serving are as follows: 7; 7; 10; 7; 9; 9. Assume the underlying distribution is approximately normal.

NOTE: If you are using a Student's t-distribution, you may assume that the underlying population is normally distributed. (In general, you must first prove that assumption, though.)

a) Construct a 90% confidence interval for the population mean grams of fat per serving of chocolate chip cookies sold in supermarkets.

(i) State the confidence interval. (Round your answers to two decimal places.)

(____,____)

a/2=____ C.L=______ a/2________

c.(iii) Calculate the error bound. (Round your answer to two decimal places.)

Answer 1

mean = sum of all terms / number of terms = 49/ 6 = 8.17

standard deviation

data	data-mean	(data - mean)2
7	-1.1667	1.36118889
7	-1.1667	1.36118889
10	1.8333	3.36098889
7	-1.1667	1.36118889
9	0.8333	0.69438889
9	0.8333	0.69438889

mean= 8.17 s =1.3292

t value for 90% of confidence interval at 6 df is TINV(0.10,5) = 2.015

Error bound = 1.09

CI = mean +/ - E = 8.17 +/- 1.09

Confidence interval = (7.07 , 9.26)