3. Much concern has been expressed in recent years regarding the practice of using nitrates as meat preservatives. In one study involving the possible effects of these chemicals, bacteria cultures were grown in a medium containing nitrates. The rate of uptake of radio-labeled amino acid was then determined for each one, yielding the following observations: 7251 6871 9632 6866 9094 5849 8957 7978 7064 7494 7883 8178 7523 8724 7468
Suppose it is known that the true average uptake for cultures without nitrates is 8000. Does the data suggest at the 1% level of significance, that the addition of the nitrates results in a decrease in true average uptake? 

4. An automobile manufacturer who wishes to advertise that one of its models achieves 30 miles per gallon decides to carry out a fuel efficiency test. Six non- professional drivers are selected. Each one drives a car from Phoenix to Los Angeles. The resulting mile per gallon figures are: 27.2 29.3 31.2 28.4 30.3 29.6
Does the data contradict the claim that the true average fuel efficiency is 30mpg? Test this at the 1% level of significance.