Question

thirty-one randomly selected students scores on the test in MTH
243 were recorded. This sample had a mean of 73 and a standard
deviation of 8.4. Construct a 98% confidence interval for the mean
score of all students MTH 243 test score. (round all values to
three decimal places)

Does this sample satisfy the conditions for constructing a
confidence interval?

Select an answer Yes No Why do you keep asking these questions of
me?

What critical value is appropriate for this problem?

Select an answer critical t-value critical z-value

What is the value of the critical value? (just enter the
number)

What is the margin of error?

E=E=

State the 98% confidence interval.

<μ<<μ<

Answer #1

Yes, this samples are randomly selected i.e samples are iid's

Critical value t(α/2, n-1) = t(0.02 /2, 31- 1 ) =
2.457

Margin of Error = t(α/2, n-1) S/√(n) = 3.707

Confidence Interval

X̅ ± t(α/2, n-1) S/√(n)

t(α/2, n-1) = t(0.02 /2, 31- 1 ) = 2.457

73 ± t(0.02/2, 31 -1) * 8.4/√(31)

Lower Limit = 73 - t(0.02/2, 31 -1) 8.4/√(31)

Lower Limit = 69.293

Upper Limit = 73 + t(0.02/2, 31 -1) 8.4/√(31)

Upper Limit = 76.707

**98% Confidence interval is ( 69.293 , 76.707
).**

16 students were randomly selected from a large group of
students taking a certain calculus test. The mean score for the
students in the sample was 86 and the standard deviation was 1.3.
Assume that the scores are normally distributed. Construct a 98%
confidence interval for the mean score, μ, of all students taking
the test. Round your answer to two decimal places.

16 students were randomly selected from a large group of
students taking a certain calculus test. The mean score for the
students in the sample was 86 and the standard deviation was 1.2.
Assume that the scores are normally distributed. Construct a 98%
confidence interval for the mean score, μ, of all students taking
the test. Round your answer to two decimal places.
a- (85.30 , 86.70)
b- (85.22 , 86.78)
c- (85.36 , 86.64)
d- (85.28 , 86.72)

Thirty randomly selected students took the calculus final. If
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construct a 99% confidence interval for the mean score of all
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What is the 95% confidence interval for the
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Critical error=
Margin of error=
confidence interval=

A sample of 25 randomly selected students has a mean test score
of 81.5 with a standard deviation of 10.2. Assuming that the
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construct a 95% confidence interval for the population mean μ of
all test scores.
A. (77.29, 85.71)
B. (56.12, 78.34)
C. (87.12, 98.32)
D. (66.35, 69.89)

The scores for the test # 3 for Abe’s stat class from 9 randomly
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By using 95% confidence level, find the confidence interval for the
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2. The principal randomly selected six students to take an
aptitude test. Their scores (from a normal distribution) were:
83.0 84.1 83.5 83.7 84.1 73.5
a. Determine a 90 percent confidence
interval for the mean score for all students. Show all
work. Identify the standard error, and all calculations
of the margin of error. Does it appear as if the mean score was
better than 84? Write the findings as you would in a
report (interpret the interval.)
b.Assume now that sigma was...

Randomly selected students participated in an experiment to test
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____<μ<_____

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students.
What is the 90% confidence interval for the population mean
μ?

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