In a survey, 28 people were asked how much they spent oh were roughly bell-shaped with a mean of $49 and standard deviation of $8. Construct a confidence interval at a 80% confidence level. Give your answers to one decimal place. 土 Interpret your confidence interval in the context of this problem.

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Question 8
In a survey, 28 people were asked how much they spent on their child's last birthday gift. The results
were roughly bell-shaped with a mean of $49 and standard deviation of $8. Construct a confidence
interval at a 80% confidence level.
Give your answers to one decimal place.
士
Interpret your confidence interval in the context of this problem.
Transcribed Image Text:Question 8 In a survey, 28 people were asked how much they spent on their child's last birthday gift. The results were roughly bell-shaped with a mean of $49 and standard deviation of $8. Construct a confidence interval at a 80% confidence level. Give your answers to one decimal place. 士 Interpret your confidence interval in the context of this problem.
Expert Solution
Step 1

Given Information:

Sample size (n) = 28

Mean x¯= 49

Standard deviation s= 8

Confidence level = 80% = 0.80

 

Since, sample size is less than 30 and the distribution is roughly bell shaped, t-distribution would be appropriate:

Significance level α=1-0.80=0.20

Confidence interval is obtained using the formula:

C.I=x¯±t*sn

Using t-table, critical value at degrees of freedom df=n-1=28-1=27 80% confidence level or 0.20 significance level is 1.314

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