fries. Potatoes are kept refrigerated before being cut for french fries to prevent spoiling and preserve flavor. But immediate processing of cold potatoes causes discoloring due to complex chemical reactions.

The potatoes must therefore be brought to room temperature before processing. Researchers want to design an experiment in which tasters will rate the color and flavor of french fries prepared from several groups of potatoes. The potatoes will be freshly picked or stored for a month at room temperature or stored for a month refrigerated. They will then be sliced and cooked either immediately or after an hour at room temperature.

(a) Identify the experimental units, the explanatory and response variables, and the treatments.

(b) The researchers plan to use a completely randomized design. Describe how they should assign treatments to the experimental units if there are 300 potatoes available for the experiment.

(c) The researchers decided to do a follow-up experiment using sweet potatoes as well as regular potatoes.

Describe how they should change the design of the experiment to account for the addition of sweet potatoes.