An experiment is done on 90 people to test their vitamin D levels: 30 are given vitamin D tablets, 30 are told to spend 15 minutes in the sun each day and 30 are kept inside and not given any supplements. What is the control group? What is the dependent variable? What is the independent variable?

The correct answer is -

The control group: the group of people with no supplements and kept inside.

The dependent variable: Vitamin D level in all groups.

The independent variable: the source of vitamin D (sun or tablets)

Explanation:

The control group of any experiment is the group of subjects that did not receive any type of treatment or did not manipulate by the independent variable. Here the group of 30 people that kept inside and did not get supplements is the control group.

The independent variable is a variable that directly affects the dependent variable by a change in the independent variable. In this experiment, the sunlight and vitamin D tablets are independent variables that affect the vitamin D level in people.

The dependent variable is a variable that is affected by the independent variable or depends on the independent variable, vitamin level is the dependent variable.

the answer is b: 1.4 km/hr