Question

Confidence Interval. Calculate a 80% confidence interval to estimate the population mean using the following data: Sample mean = 20, sample standard deviation =5, sample size = 16. Do not forget conclusion.

Answer #1

Confidence interval for Population mean is given as below:

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

From given data, we have

n = 16

df = n – 1 = 15

Confidence level = 80%

Critical t value = 1.3406

(by using t-table)

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

Confidence interval = 20 ± 1.3406*5/sqrt(16)

Confidence interval = 20 ± 1.6758

Lower limit = 20 - 1.6758 = 18.324

Upper limit = 20 + 1.6758 = 21.676

Confidence interval = (18.324, 21.676)

We are 80% confident that the population mean will lies between 18.324 and 21.676.

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standard deviation of 9.5.
Preliminary:
Is it safe to assume that n≤0.05 of all subjects in the
population?
No
Yes
Is n≥30
No
Yes
Confidence Interval: What is the 80% confidence
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inequality values accurate to one decimal place.
<μ<

Estimate the population mean by finding a 80% confidence
interval given a sample of size 54, with a mean of 36.1 and a
standard deviation of 10.8.
Preliminary:
Is it safe to assume that n≤0.05n≤0.05 of all subjects in the
population?
Yes
No
Is n≥30n≥30?
Yes
No
Confidence Interval: What is the 80% confidence
interval to estimate the population mean? Enter your answer as
an open-interval (i.e., parentheses) accurate to
one decimal place.
80% C.I. =

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confidence interval estimate that has a margin of error of plus or
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630, what is the required sample size?
The sample size must be at least?

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±44.0 If the population standard deviation is thought to be
610, what is the required sample size?

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mean using the accompanying data. What assumptions need to be made
to construct this interval?
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What assumptions need to be made to construct this
interval?
A. The sample size is less than 30.
B. The population must be normally distributed.
C. The population is skewed to one side.
D. The population mean will be in the confidence interval.

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Standard deviation ?=11
________<?__________

Use the given data to find the 95% confidence interval estimate
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Assume that the population has a normal distribution.
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Sample size ?=25
Mean ?⎯=104
Standard deviation ?=12
= ...<?<...

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Mean x¯=106 Standard deviation s=12
______<μ<________

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