DrBloedorn Is a Health Psychologist Who Researches Nutrition

Multiple Choice

Dr.Bloedorn is a health psychologist who researches nutrition.She is curious as to whether a new drink additive will help people consume fewer calories during a meal.The drink additive is a white,odorless,tasteless powder that a person can add to any drink.She collects a random sample of 63 overweight students on campus and measures the calories they eat during lunch,using a bomb calorimeter.She then gives this additive to the same 63 participants to use at dinner and measures how many calories they eat (again,using the bomb calorimeter) .

-The addition of a group that does not use the drink additive but adds a similar-looking substance that they think is the additive would help Dr.Bloedorn address which of the following threats to internal validity?

A) History
B) Observer bias
C) Instrumentation
D) Placebo effects