Researchers who were studying plant growth raised plants in two separate rooms.One room had taped conversations playing 24 hours a day; the other room was silent.The researchers found that the plants grew better in the room that had the conversations playing.In this study,what would you call the type of room (silent versus conversation)

A)  placebo 
B)  independent variable 
C)  dependent variable 
D)  extraneous variable

The type of room (silent versus conversation) is the independent variable because it is the variable that is being manipulated by the researchers to see the effect on the dependent variable (plant growth). A dependent variable is the variable that is being measured for changes as a result of the independent variable, while an extraneous variable is a variable that could potentially affect the results but is not being intentionally manipulated by the researchers. A placebo is a treatment or substance that has no therapeutic effect, but is given as if it does, typically used as a control in experiments.