18. When we conduct an experiment the condition we are investigating the one thing we want to know about is called the

a. question

b. hypothesis

c. control group

d. variable

19. The group of experimental subjects that is left "natural" or left unchanged is called the

a. control group

b. experimental group

c. hypothetical group

d. testable group

20. The group of experimental subjects that has the one condition changed is the

a. control group

b. experimental group

c. hypothetical group

d. testable group

21. When the experiment is complete the researcher

a. starts another experiment

b. researches new questions

c. analyzes the data and comes to a conclusion

d. repeats the experiments for validity

The correct answer will be option-

18. option-B hypothesis

19. option - A control group

20. option - B experimental group

21. option - C analyzes the data and comes to a conclusion

Explanation:

A scientific experiment is a systematic approach to understand and explain the natural events which include various sequential steps.

In question 18, the experiment is conducted to test the well-educated guess based on the background research which explains the phenomenon to a limited extent. This proposed statement is known as the hypothesis and is the answer.

in question 19, the sample group which is left undisturbed or in which the variable to be tested is missing is known as the control group and thus is the correct answer.

in question 20, the sample group in which the independent variable is changed which influence the dependent variable is known as the experimental group.

In question 21, after the experiment, the next step will be the analysis of the collected data from which the conclusion is drawn and is the correct answer.