Arandom sample of the closing stock prices in dollars for a company in a recent year is listed below. assume that sigma is $2.15. construct the 90% and 99% confidence intervals for the population mean. interpret the results and compare the widths of the confidence intervals. 18.41 19.11 18.67 18.97 21.97 17.26 18.69 16.73 21.97 16.43 21.97 21.66 18.77 17.93 15.47 16.44 the 90% confidence interval is

[ 17.8941, 19.6621]

Step-by-step explanation:

Given:

widths :

18.41 19.11 18.67 18.97 21.97 17.26 18.69 16.73 21.97 16.43 21.97 21.66 18.77 17.93 15.47 16.44

Total number of observations = 16

Mean of the sample =

=

= 18.7781

For 90% confidence level, z value = 1.645

Therefore,

Margin of error, E =

=

= 0.884

thus,

Confidence interval = Mean ± E

or

Confidence interval = [18.7781 - 0.884 , 18.7781 + 0.884  ]

= [ 17.8941, 19.6621]

a

step-by-step explanation:

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the answer is c.

step-by-step explanation: