Question

a Research has shown that patients' expectations of treatment effectiveness are affected by what a treatment provider is wearing. A white lab coat tends to increase their expectation of effectiveness. Gloria, a research assistant, had no preconceived ideas about her research project,
but by chance she wore a white lab coat when working with experimental Group but jeans and a t-shirt when working with experimental Group 2. This created a confounding variable. This confounding variable was a

A. Random effect
B. Placebo effect
C. Selection effect
D. Experimenter effect

Answer 1

If patients' expectations of the treatment effectiveness are affected by what a treatment provider is wearing, thereby causing a confounding variable, this confounding variable was a B. Placebo effect.

Placebo effect arises from a conviction that the administered treatment is real and effective, whereas it is not.  

Random effect refers to the effect caused by a random variable. Selection effect raises a validity problem because of a selection bias. Just like a selection effect, an experimenter effect also causes a bias that affects the validity of an experiment.

Thus, a placebo effect is a confounding variable that can lead to a misleading or an unexpected or unintended result.

Read more about placebo effect at https://brainly.com/question/19705501