The changing ecology of swamps has been the subject of much environmental research. One water-quality parameter of concern is the total phosphorous level. Suppose that the Ministry of the Environment makes 15 measurements in one area of the swamp, yielding a mean level of total phosphorus of 12.3 parts per billion (ppb) and a standard deviation of 5.4 ppb. The Ministry wants to test whether the data support the conclusion that the mean level is less than 15 ppb. Assume measurements are normally distributed.
-How much evidence do we have that the mean level of phosphorus is less than 15 parts per billion?
A)No evidence
B)Some evidence
C)Strong evidence
D)Very strong evidence
E)Extremely strong evidence

Question

Quizplus · Accepted Answer

The sample mean is 12.3 ppb, which is less than 15 ppb. A t-test can be used to determine the evidence strength. With a sample size of 15, the t-statistic is calculated, and the p-value indicates some evidence against the null hypothesis that the mean is 15 ppb.

The Changing Ecology of Swamps Has Been the Subject of Much