We want to evaluate dog owners' reactions to a new dog food product formulation that contains more vegetables.

An experiment is conducted where five stores are chosen in each of two regions (A and B) with similar sales for the original formulation. In region A, the shelves are stocked with both formulations. In region B, the stores are stocked with only the original formulation. The package of the new formula is exactly the same as the original formula except for three modifications: the color is changed (from blue to green), the content label is changed, and a yellow banner with black letters "More vegetables!" diagonally crosses the upper left corner of the bag. For a six-month period before and after the new product formula introduction, sales of the original version are recorded in all ten stores; for the six months after the new product formulation, sales of the more-vegetable formula in the five stores are recorded.

For the dog food test market experiment, rather than selecting two regions (A and B) with similar sales levels, assume that you instead chose five stores in region C (a high-sales region) to compare to five stores in region D (a low-sales region). 

Which of the following factors might affect the study's internal validity?

Maturation

Instrumentation

Selection

Regression toward the mean

Experimental mortality

Answer rating: 100% (QA)

Internal validity is the degree to which the observed results accurately reflect the population we a... View the full answer