A researcher wishes to estimate the percentage of adults who support abolishing the penny. What size sample should be obtained if he wishes the estimate to be within 3 percentage points with 99​% confidence if he uses a previous estimate of 25​%(?) and if he he does not use any prior​ estimates?

The Student Health Center at NCSU would like to conduct a survey to estimate the proportion of NCSU students who have smoked marijuana in the past month. The Student Health Center would like to estimate the population proportion p to within .04 with 95% confidence. 1. What sample size is required if the Health Center has no knowledge of the approximate value of p? 2. The Health Center discovers the results of a previous survey that estimates p to be about .35. Use this additional information to calculate the sample size required to estimate the population proportion p to within .04 with 95% confidence.

If n = 20, the sample mean = 250, SD = 15, SEM = 3.354, what is the confidence interval (using 95% confidence level). What percent confidence do you have that the population mean is between what two values

The state education commission wants to estimate the fraction of tenth grade students that have reading skills at or below the eighth grade level. In an earlier study, the population proportion was estimated to be 0.22. How large a sample would be required in order to estimate the fraction of tenth graders reading at or below the eighth grade level at the 90% confidence level with an error of at most 0.03? Round your answer up to the next integer.