large population of 5,000 students take a practice test to prepare for a standardized test. The population mean is 140 questions correct, and the standard deviation is 80. What size samples should a researcher take to get a distribution of means of the samples with a standard deviation of 10?    provide the solution of above questions

In the past, the mean age of consumers of a product was 38 years. Recently the product has been drastically changed. In order to determine whether there has been a change in the mean age of the product consumers, a sample of 16 consumers is selected. The mean age in the sample is 33 years and the standard deviation in the sample is 10 years. Let u = the mean age of the current product (Problem Set #7) consumers. The value of the test statistic is Oa. -2.00 O b.-1.60 OC .0.8 O d. 4.21

A marketing specialist wants to estimate the average amount spent by visitors to an online retailer's newly-designed website. From the data in a preliminary study she guesses that the standard deviation of the amount spent is about 14 dollars. Question 1. How large a sample should she take to estimate the mean amount spent to within 5 dollars with 95% confidence? (Round your answer up to the next largest integer).

I need help solving this problem.

You determine that the standard deviation for a sample of test scores is 0.  This tells you that 1 all the test scores must be 0. 2 all the test scores must be the same value. 3 there is no straight-line association. 4 the mean test score must also be 0. 5 you made a mistake because the standard deviation can never be 0.

Solve question 5. Show work for it aswell please with the steps.

You are given the following information:  sample mean is equal to 103.55, population standard deviation is equal to 14.88, sample size is equal to 111 and the national average is equal to 109.  What would be the value of z-observed?