If the confidence level is decreased and the standard deviation and sample size stay the same, then the Error will be increased. True False

Prob & Stats  Unable to solve 90% confidence interval of the differences in the nurses.

A recent study of 28 randomly selected employees of a company showed that the mean ofdistance they traveled to work was 14.3 miles. The standard deviation of the sample was 2.0miles. Find the 95% confidence interval of the true mean.

Suppose we wish to calculate a 90% confidence interval for the average amount spent on books by freshmen in their first year at a major university. The interval is to have a margin of error of $2. Assume that the amount spent on books by freshmen has a normal distribution with a standard deviation of $30. How many observations are required to achieve this margin of error?

A professor wants to estimate how many hours per week her students study. A simple random sample of 72 students had a mean of 19 hours of studying per week. Construct a 90% confidence interval for the mean number of hours a student studies per week. Assume that the population standard deviation is known to be 2.1 hours per week. Round to two decimal places.

Do AP Statistics students have higher GPA's than non AP Statistics students? Random samples of 20 AP Statistics students and 20 non AP Statistic students were taken. AP Statistics students had a mean GPA of 3.335 with a standard deviation of 0.557. Non AP Statistics students had a mean GPA of 3.04 with a standard deviation of 0.685. Assume the distribution of all AP Statistics scores are normally distributed. Use a 95% confidence interval for the true difference in average GPAS for AP Statistics and non AP Statistics students to determine if one group has a higher GPA than the other.

A random sample of 64 shoppers showed that they spend an average of $27.31 per visit at the Sunday Mornings Bookstore. The standard deviation of the population is $2.14. Find the 90% confidence interval of the true mean. Please include all work showing how you found your answer.

Christina wants to know the true average number of pages in a typical textbook. She randomly selects 196 books, and they have an average of 161 pages. Calculate a 90.3% confidence interval if you are given that the standard deviation for a single book is 75 pages.

A recent survey of 25 students showed that they spent an average of $18.53 on petrol eachweek. The standard deviation of the sample was $3.00. Find the 99% confidence intervalfor the true mean (average over all students).

Researchers wants to determine if low-fat diets or low-carb diets are more effective for weight loss. Suppose 100 people were placed on a low-fat diet and at the end of 3 months the mean weight loss was 10.5 lbs witha standard deviation of 12.5 lbs. There were another 100 people placed on a low-carb diet and at the end of 3 months the mean weight loss was 16.5 lbs with a standard deviation of 10.2 lbs. Does mean weight lossdiffer between the two diets? What are the hypotheses??