A chemical engineer found that by adding different amounts of an additive to gasoline, she could reduce the amount of nitrous oxides (NOx) coming from an automobile engine. A specified amount will be added to a gallon of gas and the total amount of NOx in the exhaust collected. Initially, five runs with 1,2,3,4, and 5 units of additive will be conducted.

(a) How would you randomize in this experiment?

(b) Suppose you properly calculate a point estimate of the mean value of NOx when the amount of additive is 8 . What additional danger is there in using this estimate?