Question

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 known to be 4.17. What is the confidence interval for the mean score? Show your work. How is it different above? Why?

Answer #1

the national average for the 7th grade aptitude test in 2004 was
85. The principal at O'Farrell Middle School feels that the averagr
for his students this year will be different. He randomly selected
10 students to take the aptitude test. Their scores were: 83.4 72.1
89.2 83.3 85.9 79.2 80.3 88.5 90.1
1- state the sample mean and mean and sample standard
deviation.
2- Determine 95% confidence interval
3- Does this confidence interval suggest that the average score
of...

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...

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)

A group of 51 randomly selected students have a mean score of
29.5 with a sample standard deviation of 5.2 on a placement test.
What is the 95% confidence interval for the
mean score, μ, of all students taking the test?
Critical error=
Margin of error=
confidence interval=

The data set represents the scores of 12 randomly selected
students on the SAT Physics Subject Test. Assume the population
test scores are normally distributed and the population standard
deviation is 103. (Adapted from The College Board) 670 740 630 620
730 650 720 620 640 500 670 760
(a) Find the point estimate of the population mean.
(b) Construct a 90% confidence interval for the population mean.
Interpret the results.
(c) Determine the minimum sample size required to be...

A principal claims the students in his school have above-average
test scores for a particular standardized test.
A sample of 50 students from his school were found to have an
average test score of 77.2.
The population mean for test scores for this particular test is
75, with a standard deviation of 9 (so we can assume that the
population test score is normally distributed).
Set up a hypothesis test to determine whether this principal’s
claim is correct (use alpha...

The scores for the test # 3 for Abe’s stat class from 9 randomly
selected students are as such 86 ,70, 95, 90, 77, 88, 85, 92, 90.
By using 95% confidence level, find the confidence interval for the
average test score for test # 3 for all Abe’s stat class.
7) A) E =5.85 B) E = 6.28 C) E =6.02 D) E = 5.89
8) A) 79.87 < < μ 91.91 B) 83.24 < < μ 121.27 C)...

2. Suppose a new standardized test is given to 100 randomly
selected third-grade students in New Jersey. The sample average
score, Y¯ , on the test is 58 points, and the sample standard
deviation, sY , is 8 points. (a) Construct a 95% confidence
interval for the mean score of all New Jersey third graders.
(b) Suppose the same test is given to 200 randomly selected
third graders in Iowa, producing a sample average of 62 points and
a sample...

10) The SAT scores for 12 randomly selected seniors at a
particular high school are given below. Assume that the SAT scores
for seniors at this high school are normally distributed.
867
1,234
894
1,264
614
861
1,382
968
824
944
702
1,360
a) Find a 95% confidence interval for the true mean SAT score
for students at this high school.
b) Provide the margin of error of the interval
as your answer.
Round your answer to the nearest whole...

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