# INFERENTIAL STATISTICS

PART 2: INFERENTIAL STATISTICS

1. Randomly select a large sample (at least 30 data values) from the data set. Describe clearly the
method of selecting the random sample. -5 pts-

2. Calculate the sample mean and sample standard deviation for your sample and compare these to your
population mean and population standard deviation. -5 pts-

3. Calculate 80%, 90% and 99% confidence intervals for the mean, assuming you know the
population standard deviation. You may calculate all three intervals using the TI-83 or TI-84
calculator. Be sure to give the intervals and explain exactly what they mean. -10 pts-

How does this relate to the population mean you calculated in part 1 of the project, when the set of data
was treated as a population where you knew the standard deviation? -5 pts-

4. Calculate 80%, 90% and 99% confidence intervals for the mean, assuming that you don’t know
the population standard deviation. You may calculate all intervals using the TI-83 or TI-84
calculator. Be sure to give the intervals and explain exactly what they mean -10 pts-

How does this relate to the population mean you calculated in part 1 of the project, where you are now
pretending to not know the population standard deviation? -5 pts-