# Statistic

Researchers collected samples of water from streams in a mountain range to investigate the effects of acid rain. They measured the pH (acidity) of the water (a lower pH means the water is more acidic). They then classified the steams with respect to the kind of substrate (type of rock on which they flow). Here are the results:

Substrate Size Mean StandardDeviation Limestone 41 7.7 2.2
Shale 33 6.8 1.7

-Is there sufficient evidence that there is a significant difference in the acidity of streams that flow on limestone and on shale?

a. What is (are) the parameter(s) we are conducting inference on? Choose one of the following symbols (mean; meanDifferent (the mean difference from a matched pairs design); mean1 - mean2 (the mean difference from independent samples); p, or p1 – p2) and describe it in words.

b. Are the conditions satisfied? Why or why not?
If the answer to part b is no, do not complete the rest of #2.

c. At the 0.05 significance level, can the researcher conclude from these data that there is a significant difference between the mean acidity of the streams that flow on limestone and on shale?
i.State the null and alternative hypotheses.
ii.State the significance level for this problem.
iii.Calculate the test statistic.
iv.Calculate the P-value and include the probability notation statement.
v.State whether you reject or do not reject the null hypothesis.
vi.State your conclusion in context of the problem (i.e. interpret your results).

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