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

Question

Quizplus · Accepted Answer

The addition of a group that adds a similar-looking substance that they think is the additive would help Dr. Bloedorn address the placebo effect, which is the tendency for participants to positively respond to a treatment due to their belief in its effectiveness rather than the actual properties of the treatment. By having a control group that receives a similar-looking substance without the active ingredient, Dr. Bloedorn can control for the placebo effect and observe the actual effect of the drink additive. This would not necessarily address history, observer bias, or instrumentation.

Dr Bloedorn Is a Health Psychologist Who Researches Nutrition