An industrial company claims that the mean pH level of the water in a nearby river is 6.8.

To test this claim you randomly select 19 water samples and measure the pH of each.

The sample mean is 6.7, and the standard deviation of the sample is 0.24.

At the .05 significance level, does this sample provide evidence to refute the company's claim?

a. Yes, because the p-value is less than the significance level.

b. No, because p = .0860 is greater than .05.

c. No, because -1.816 is less than the p-value

d. Yes, because the test statistic is less than the significance level.