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Answer:
Answer:
Critical value: T = 1.34
Lower endpoint: $63.04
Upper endpoint: $102.86
Step-by-step explanation:
We are in posession of the sample's standard deviation, so we use the student t-distribution to solve this question.
The first step to solve this problem is finding how many degrees of freedom, we have. This is the sample size subtracted by 1. So
df = 17 - 1 = 16
80% confidence interval
Now, we have to find a value of T, which is found looking at the t table, with 16 degrees of freedom(y-axis) and a confidence level of ). So we have T = 1.34 as our critical value.
The margin of error is:
M = T*s = 1.337*14.89 = 19.91.
In which s is the standard deviation of the sample.
The lower end of the interval is the sample mean subtracted by M. So it is 82.95 - 19.91 = $63.04
The upper end of the interval is the sample mean added to M. So it is 82.95 + 19.91 = $102.86