Much concern has been expressed regarding the practice of using nitrates as meat preservatives. In one study involving possible effects of these chemicals, bacteria cultures were grown in a medium containing nitrates. The rate uptake of radio-labeled amino acid was then determined for each culture, yielding the following observations:

Suppose that it is known that the true average uptake for cultures without nitrates is 8,000. Do these data suggest that the addition of nitrates results in a decrease in the mean uptake? Test the appropriate hypotheses using a significance level of 0.10.

7,251 6,871 9,632 6,866 9.094 5,849 8,957 7.978 7,064 7.494 7,883 8.178 7,523 8,724 7.468