A population has a mean of 800 and a standard deviation of 200.Suppose a sample of size 400 is selected and x is used to estimateμ. (Round your answers to four decimal places.)
(a) What is the probability that the sample mean will be within±5 of the population mean?
(b) What is the probability that the sample mean will be within±10 of the population mean?
A simple random sample of 90 items resulted in a sample mean of70. The population standard deviation is
σ = 15.
(a)
Compute the 95% confidence interval for the population mean.(Round your answers to two decimal places.)
to
(b)
Assume that the same sample mean was obtained from a sample of180 items. Provide a 95% confidence interval for the populationmean. (Round your answers to two decimal places.)
to
(c)
What is the effect of a larger sample size on the intervalestimate?
A larger sample size provides a smaller margin of error.A largersample size provides a larger margin oferror.    A larger sample size does not changethe margin of error.
