A ____ from a sample is used to estimate a population _____. The two words that best fill these blanks are:
An engineer wants to try two hardening ovens to see whether they have different hardness scores. She cuts 8 pieces of bar stock in half, putting half of each in oven A and the other half in oven B. The following data are collected:
Do the data indicate that the ovens have different average scores? Assume differences are normally distributed.