Final answer:
A controlled experiment is an investigation where one independent variable is manipulated under controlled conditions to observe its effect on a dependent variable, testing a hypothesis.
Step-by-step explanation:
The type of investigation described is known as a controlled experiment. An experiment is where a researcher manipulates an independent variable and observes the effect on a dependent variable, under carefully controlled conditions to test a hypothesis. It involves manipulating the independent variable to see how it affects the dependent variable. The goal of an experiment is to isolate the cause of the experimental results by controlling other factors. Only one independent variable is changed at a time to ensure that the outcomes observed are solely due to the modification of that variable, while other potential influence factors, known as control variables, are kept constant.