# assignment questions

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Express the confidence interval using the indicated format.
Express the confidence interval 0.047 < p>

Assume that a sample is used to estimate a population proportion p. Find the margin of error E that corresponds to the given statistics and confidence level. Round the margin of error to four decimal places. 95% confidence; n = 320, x = 60

Determine whether the samples are independent or dependent.
The effectiveness of a headache medicine is tested by measuring the intensity of a headache in patients before and after drug treatment. The data consist of before and after intensities for each patient.

Construct the indicated confidence interval for the difference between the two population means. Assume that the two samples are independent simple random samples selected from normally distributed populations. Do not assume that the population standard deviations are equal.
A researcher was interested in comparing the GPAs of students at two different colleges. Independent simple random samples of 8 students from college A and 13 students from college B yielded the following GPAs.

College
A 3.7, 3.2, 3.0, 2.5, 2.7 ,3.6, 2.8, 3.4

College B: 3.8,2.8,3.2,4.0,3.0,3.6,3.9,2.6,3.8,4.0,2.5,3.6,3.9
Construct a 95% confidence interval for , the difference between the mean
GPA of college A students and the mean GPA of college B students.

Question 31:-
Use the given degree of confidence and sample data to find a confidence interval for the population standard deviation σ. Assume that the population has a normal distribution. Round the confidence interval limits to the same number of decimal places as the sample standard deviation. The mean replacement time for a random sample of 20 washing machines is 9.4 years and the standard deviation is 2.6 years. Construct a 99% confidence interval for the standard deviation, σ, of the replacement times of all washing machines of this type.

Qn32:
Determine whether the samples are independent or dependent.
The effectiveness of a new headache medicine is tested by measuring the amount of time before the headache is cured for patients who use the medicine and another group of patients who use a placebo drug.

Qn33:-
Assume that a sample is used to estimate a population proportion p. Find the margin of error E that corresponds to the given statistics and confidence level. Round the margin of error to four decimal places.

98% confidence; the sample size is 890, of which 25% are successes.

Qn34:-
Use the confidence level and sample data to find the margin of error E. Round your
answer to the same number of decimal places as the sample mean unless otherwise
noted.

Systolic blood pressures for women aged 18-24: 94% confidence;