Question

Listed below are the ages (years) of randomly selected race car drivers. Construct an 80% confidence interval estimate of the mean age of all race car drivers :

32, 32, 33, 33, 41, 29, 38, 32, 33, 23, 27, 45, 52, 29, 25

Answer #1

Confidence interval for Population mean is given as below:

Confidence interval = Xbar ± t*S/sqrt(n)

From given data, we have

Xbar = 33.6

S = 7.669978581

n = 15

df = n – 1 = 14

Confidence level = 80%

Critical t value = 1.3450

(by using t-table)

Confidence interval = Xbar ± t*S/sqrt(n)

Confidence interval = 33.6 ± 1.3450*7.669978581/sqrt(15)

Confidence interval = 33.6 ± 2.6637

Lower limit = 33.6 - 2.6637 = 30.94

Upper limit = 33.6 + 2.6637 = 36.26

Confidence interval = (30.94, 36.26)

Listed below are the ages (years) of randomly selected race car
drivers. Construct an 80% confidence interval estimate of the mean
age of all race car drivers. 32 32 33 33 41 29 38 32 33 23 27 45 52
29 25.

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29
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Age
Under 25
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Over 64
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97
62
38
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37
33
38
24
48
41
39
38
15
26
20
41
37
25
11
28
35
33
28
31
40
30
48
42
25
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c) How would the confidence interval change if you had assumed
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33
28
33
37
31
32
31
28
34
28
33
26
30
31
28
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Point Estimate:
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42 45 24 32 41
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