A physics lab instructor wants to estimate the time required for physic students to complete a required experiment.  From a previous study she found the population standard deviation to be 16 min. How large a sample is required to be 90% confident that the point estimate is within 5 min of the population mean time

A large population of 5,000 students take a practice test to prepare for a standardized test. The population mean is 146 questions correct, and the standard deviation is 70. What size samples of students should a researcher take to get a distribution of means of the samples with a standard deviation of 10?

A psychologist wants to estimate the amount of math anxiety that the population of high school students experience prior to taking their first algebra course. On the first day of class he asks a sample of 36 students to answer the question, “How anxious do you feel when you know you have to do math problems?” They each responded using a 100-point scale with 1 = not at all anxious and 100 = extremely anxious. The mean reported anxiety score for this sample was 58 with a standard deviation of 30 Compute the upper and lower boundaries for this 95% confidence interval.     LB = 66.45, UB - 49.55     LB = 28, UB = 88     LB = -5.00, UB = 5.00     LB = 47.86, UB = 68.15     LB = -10.15, UB = 10.15

Researchers want to estimate the IQ scores for 3 year old children. It is known from a previous study that the standard deviation of IQ scores is approximately 20 for this age group. How many such children should the researchers sample in order to estimate the average IQ score for all 3 year olds within 5 points with 95% confidence? Round up your answer to the nearest integer.