please help... I don't understand these

Question 6 [1 point) A financial analyst wants to determine the proportion of adults who have invested money in an IRA. Find the minimum sample size necessary to be 84% confident that the sample proportion is within 3 percentage points of the true population proportion. 54 1097 549 391 Question 7 [1 point) A financial analyst wants to determine the proportion of adults who have invested money in an IRA. Find the minimum sample size necessary to be 86% confident that the sample proportion is within 3 percentage points of the true population proportion. O 609 O 412 294 O 60a Question 8 [1 point) Find the critical value for a 90% confidence interval estimate of the mean. The data values are normally distributed, the sample size is 30, and the population standard deviation is not known. 2045 2042 1.497 1.499 Question 9 [1 point) Find the critical value for a 90% confidence interval estimate of the mean. The data values are normally distributed, the sample size is 20, and the population standard deviation is not known. 2 528 12 045 OC 2061 2.539