A physical therapist wants to determine the difference in the proportion of men and women who participate in regular sustained physical activity. What sample size should be obtained if she wishes the estimate to be within two percentage points with 99% confidence, assuming that (a) she uses the estimates of 22.3% male and 18.5% female from a previous year? (b) she does not use any prior estimates? (a) n = (b) n = (Round up to the nearest whole number.) (Round up to the nearest whole number.)

A physical therapist wants to determine the difference in the proportion of men and women who participate in regular sustained physical activity. What sample size should be obtained if she wishes the estimate to be within five percentage points with 95% confidence, assuming that (a) she uses the estimates of 22.9% male and 19.5% female from a previous year? (b) she does not use any prior estimates?

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 55 percentage points with 90​% confidence if ​(a) he uses a previous estimate of 28​%? n=what ​(b) he does not use any prior​ estimates? n=what

Suppose we know that a confidence interval for a population proportion is (0.105,0.355), with a sample proportion of p̂=0.23. What is the margin of error?

You would like to construct a 95% confidence interval to estimate the population mean annual income for people over age 40 in your state. You choose a random sample of such incomes and compute the mean of the sample as 40,346 dollars with a standard deviation of 7757 dollars. (a) What is the best point estimate, based on the sample, to use for the population mean? dollars G (b) For each of the following sampling scenarios, determine which distribution should be used to calculate the critical value for the 95% confidence interval for the population mean. (In the table, Z refers to a standard normal distribution, and refers to a t distribution.) Sampling scenario z t Could use either Z or / Unclear The sample has size 14, and it is from a normally distributed population with an unknown standard deviation. о о The sample has size 17, and it is from a population with a distribution about which we know very little. O о The sample has size 110, and it is from a non-normally distributed…

1. (a) Eight randomly selected batches of a chemical were tested for impurity concentration. The percentage impurity levels found in the sample were as follows: 5.3 6.2 4.1 5.4 3.6 5.6 4.8 (b) (c) (d) 4.2 (0) (ii) Calculate the sample mean and sample variance. Construct a 95% confidence interval for the population mean. A random sample of 35 new graduates from Bangor University shows a mean starting salary of £17,250 and a standard deviation of £3,088. Construct a 95% confidence interval for the population mean starting salary. A components manufacturer claims that its average proportion of defective components is 1%. 65 defectives were found in a particular batch of 5000 components. Using the sample data, construct a 95% confidence interval for the population proportion of defectives. Provide a recommendation as to whether or not the company's claim should be believed. A loan auditor at a bank wishes to consider the loan balance for all customers who are currently carrying overdrafts.…

Suppose that you are interested in the number of people in each household in the U.S. Your sample includes 10 households, with a mean 2.5 and a standard deviation 1.2. Construct a 95% confidence interval (CI) of the mean number of household members.  (A) 1.2-3.8 (B) 1.4-3.6 (C)1.6-3.4 (D) 1.7-3.3 (E) 1.8-3.2

b) Based on sample size of N=31 and sample statistics x = 50.6077 unit, s², = 1.9874 unit? determine the whole population statistics at 90% confidence level, also estimate the population mean from the sample data at 95% confidence level.

You would like to construct a 95% confidence interval to estimate the population mean score on a nationwide examination in psychology, and for this purpose we choose a random sample of exam scores. The sample we choose has a mean of 511 and a standard deviation of 71. (a) What is the best point estimate, based on the sample, to use for the population mean? X ? (b) For each of the following sampling scenarios, determine which distribution should be used to calculate the critical value for the 95% confidence interval for the population mean. (In the table, Z refers to a standard normal distribution, and t refers to a t distribution.)

Assume that all​ grade-point averages are to be standardized on a scale between 0 and 6. How many​ grade-point averages must be obtained so that the sample mean is within 0.012 of the population​ mean? Assume that a 95​% confidence level is desired. If using the range rule of​ thumb, σ can be estimated as range/4=6−0/4=1.5. Does the sample size seem​ practical?