Below is the evaluation design schematic for the Calorie Labeling evaluation (Elbel et al., 2009), which tested a policy requiring fast food restaurants in New York City to label the number calories for each food item on the menu:

O1 X O3

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O2 O4

a. State one of the primary hypotheses of the evaluation (that is, what the researchers hoped to see) using the appropriate Os from the schematic; i.e., what should be greater than what, if O = average calories in food purchased per customer? (3 points)

b. What is a plausible threat to internal validity for this study? Explain your answer