Researchers collected samples of water from streams in the Adirondack Mountains to investigate the effects of acid rain. They measured the pH (acidity) of the water and classified the streams with respect to the kind of substrate (type of rock over which they flow). A lower pH means the water is more acidic. Here is a plot of the pH of the streams by substrate (limestone, mixed, or shale):

Here are selected parts of a software analysis comparing the pH of streams with limestone and shale substrates:
2-Sample t-Test of (2 - (2 Difference Between Means = 0.735 t-Statistic = 16.30 w/133 df p ‰¤ 0.0001
a) State the null and alternative hypotheses for this test.
b) From the information you have, do the assumptions and conditions appear to be met?
c) What conclusion would you draw?

Transcribed Image Text:

8.0 F 7.6 효 72 6.8 6.4 Substrate Type