A clinical trial was conducted to test the effectiveness of a drug for treating insomnia.Before treatment,13 subjects had a mean wake time of 100 minutes.After treatment the 13 subjects had a mean wake time of 75.5 minutes and a standard deviation of 23.9 minutes. Assume that the 13 sample values appear to be from a normally distributed population and construct a 95% confidence interval estimate of the mean wake time for a population with drug treatment. What does the results suggest about the mean wake time of 100 min before treatment? Does the drug appear to be effective?

An apartment hunter is shopping for either a one-bedroom or two-bedroom apartment in varying apartment buildings. She wants to estimate the additional amount she would have to pay, on average, for a two-bedroom apartment versus a one-bedroom apartment. The table shows the prices, in dollars, for one- and two-bedroom apartments from the nine buildings she visited.   A 95% confidence interval for the true mean difference between two-bedroom and one-bedroom apartments for apartment buildings like the ones in the sample was (255.93, 508.51). A friend of the apartment hunter tells her to expect to pay about $500 more per month for a two-bedroom apartment than for a one-bedroom apartment. Does the confidence interval provide evidence for the friend’s claim? A. No, the confidence interval does not contain 0, so the friend’s claim is not plausible. B. No, the confidence interval contains many more numbers below 500 than above 500, so it is unlikely that the friend’s assertion is correct. C.…

Afra is working in a bank. She has randomly contacted 36 customers and has examined their average annual salary. She found that the average salary of this sample of customers is $68200 with a sample standard deviation of $2375. She needs to report the population average at 95% confidence interval. What is the range that she should report?

in a test of the effectiveness of garlic for lowering cholesterol, 43 subjects were treated with garlic in a processed tablet form. Cholesterol levels were measured before and after the treatment. The changes in their levels of LDL cholesterol have a mean of 5.7 and a standard deviation of 17.7. Construct a 99% confidence interval estimate of the mean net change in LDL cholesterol after the garlic treatment. What does the confidence interval suggest about the effectiveness of garlic and reducing LDL cholesterol?

Researchers from a certain country were interested in how characteristics of the spleen of residents in their tropical environment compare to those found elsewhere in the world. The researchers randomly sampled 91 males and 109 females in their country. The mean and standard deviation of the spleen lengths for the males were 10.9 cm and 0.9 cm, respectively, and those for the females were 9.8 cm and 1.1 cm, respectively. Determine a 95% confidence interval for the difference between mean spleen lengths of males and females in this country. Click here to view page 1 of the table of critical values of t. Click here to view page 2 of the table of critical values of t. Let population 1 be all males in the country and let population 2 be all females in the country. The 95% confidence interval for µ1 - 4½ is ( | D (Round to three decimal places as needed. Use ascending order.)

We asked 41 people to report the number of cars they've ever owned. The results are a mean of 4.6 and a standard deviation of 1.3. Construct a 80% confidence interval.