Question: An experiment was conducted to determine the extent to which the growth rate of a certain fungus could be affected by filling test tubes containing the same medium at the same temperature with different inert gases. Three such experiments were performed for each of six gases, and the average growth rate over these three tests was used as the response. The following table gives the molecular weight (X) of each gas used and the average growth rate (Y) in milliliters per hour for the three tests:

a) Find the least-squares estimates of slope and intercept for the straight-line regression

of Y on X.

b) Test for significant slope of the fitted straight line

c) What is the 90% confidence interval for the true average growth rate if the gas used

has a molecular weight of 100?