What is the 90% confidence interval of the mean?

A First Course in Probability (10th Edition)
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ISBN:9780134753119
Author:Sheldon Ross
Publisher:Sheldon Ross
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What is the 90% confidence interval of the mean?
Narmal
No Spacing
Heading 1
Heading 2
Title
Subtitle
Subt
Females
Balance Time
Exercise days per week Favorite Exercise
Swimming
Swimming
Walking
Jogging
1
30
4
38
4
3
32
4
23
35
Aerobics
6.
7.
28
3.
Jogging
Swimming
Swimming
32
4
8
35
2
1. The mean and standard deviation for the time in seconds for
females who participated:
Mean = 30+ 38+32+ 23+35+28+32+ 35= 253
Mean = 253/8=31.6
x-mean
x mean?
30
-1.6
38
6.4
32
0.4
23
-8.6
35
3.4
28
-3.6
32
0.4
35
3.4
SD = V153.88/8
= 4.386
= 4.4
Focus
Transcribed Image Text:Narmal No Spacing Heading 1 Heading 2 Title Subtitle Subt Females Balance Time Exercise days per week Favorite Exercise Swimming Swimming Walking Jogging 1 30 4 38 4 3 32 4 23 35 Aerobics 6. 7. 28 3. Jogging Swimming Swimming 32 4 8 35 2 1. The mean and standard deviation for the time in seconds for females who participated: Mean = 30+ 38+32+ 23+35+28+32+ 35= 253 Mean = 253/8=31.6 x-mean x mean? 30 -1.6 38 6.4 32 0.4 23 -8.6 35 3.4 28 -3.6 32 0.4 35 3.4 SD = V153.88/8 = 4.386 = 4.4 Focus
Expert Solution
Step 1

A confidence interval is an interval that has the property that is very likely that the population parameter is contained by it and this likelihood is measure by the confidence level .

The formula for a confidence interval for the population mean  when the population standard deviation is not known is

CI=x¯tα/2,n1×sn, x¯+tα/2,n1×sn 

where the value is the critical t-value associated with the specified confidence level and the number of degrees of freedom df = n -1. 

Given : 

The provided sample mean is  X¯ and the sample standard deviation is . The size of the sample isn = 8 and the required confidence level is 90%.

The number of degrees of freedom are , and the significance level is .

Based on the provided information, the critical t-value for and  degrees of freedom is 

 

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