Manisha wanted to test the eating habits of her dog. She decided to study how the amount of food and the time of giving food affects the speed at which the dog ate. What is wrong with the design of Manisha's experiment and how can she correct it?

Question

Atith Adhikari · Accepted Answer

In Manisha's experiment to test the eating habits of her dog, we can identify the following variables of scientific research:

Independent variable: amount of food, time of giving food
Dependent variable: the speed at which the dog ate

An experiment with two independent variables cannot correctly and reliably study the effects of these variables on a third variable. Hence, to correct her experiment, Manisha should do either of the following:

Independent variable: amount of food; Controlled variable: time of giving food
Independent variable: time of giving food; Controlled variable: amount of food

By doing so, she can correctly study the influence of either of these factors on the speed at which the dog ate.