statistics

Question

An IQ test is designed so that the mean is 100 and the standard deviation is 2424 for the population of normal adults. Find the sample size necessary to estimate the mean IQ score of statistics students such that it can be said with 9090?% confidence that the sample mean is within 77 IQ points of the true meanAssume that sigmaσequals=2424 and determine the required sample size using technology. Then determine if this is a reasonable sample size for a real world calculation

 

Answer 1

is sigma 24? The value 2424 can't be correct. If the mean score is around 100 a standard deviation of 2424 would mean that there are negative IQ's. While I know some people who I think might have negative IQ's. Neither does 77 IQ points sound correct. Perhaps 7 points is correct.