Scientists and engineers

Scientists and engineers frequently wish to compare two different techniques for measuring or determin- ing the value of a variable. In such situations, interest centers on testing whether the mean difference in measurements is zero. The  article  Evaluation of the Deuterium Dilution Technique Against the Test Weighing Procedure for the Determination of Breast Milk Intake (Amer. J. Clin. Nutrit., 1983: 996—1003) reports the accompanying data on mea- suring amount of milk ingested by each of 14 randomly selected infants.

a.   Is it plausible that the population distribution of differences is normal?

b.   Does it appear that the true average difference between intake values measured by the two methods is something other than zero? Deter- mine the P-value of the test, and use it to reach a conclusion at signi cance level .05.

c.    What happens if the two-sample test is (incor- rectly) used? Hints1 = 352.970,s2 = 234.042.

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