Question

Hakeem is testing the effects of sunlight on samples of soil. Which of these actions would introduce confounding variables into Hakeem’s experiment?
He tests a theory that’s already been established.
He tests multiple hypotheses at a time.
He uses identical specimens when completing multiple trials.
He adjusts the independent variable and records the effects.
He uses different types of soil in each of his samples.

Answer 1

A confounding variable refers to an external effect, which modifies the influence of an independent and dependent variable. This extraneous effect is used to affect the outcome of an experimental design. The confounding variables can ruin the experiment and can generate unnecessary outcomes.  

In the given case, confounding variables can be introduced by testing multiple hypotheses at a time and by using distinct kinds of soil in each of the samples.  

Answer 2

Answer:

The correct answers are "He tests multiple hypotheses at a time" and "He uses different types of soil in each of his samples".

Explanation:

Confounding variables are factors that are not taken into account while performing an experiment, and can ruin the results by introducing bias or by giving false positive or negative results. Confounding variables must be avoided in any experiment, which must be designed to test only one variable at the time. In this case Hakeem would introduce confounding variables if he tests multiple hypotheses at a time or if he uses different types of soil in each of his samples. This two scenarios involve testing different variables at the same time, instead of testing just one at the time as it should be.