Biology is harmful

Question

A group of biology students tests the growth of bacteria under different conditions. The students apply the same amount of bacteria to identical Petri dishes enriched with nutrients, then place each plate at a different temperature. The bacteria are allowed to grow for three days, after which the number of bacterial colonies on each plate is counted. What is the dependent variable in this experiment?

Answer 1

In an experiment, we term the independent variable the variable that the experimenter changes. The dependent variable is the variable we measure, that may or may not change as a result of the experimenter changing the independent variable. Different temperatures are therefore the independent variable (because the experimenter changes temperature between groups), and the number of colonies would be the dependent variable (the experimenter is measuring how many colonies result from a change in the independent variable). The controls in this experiment are initial amount of bacteria, identical petri dishes, and same nutrients.