PSY 550 Final Exam Answers: Grand Canyon University

For each of the following examples, explain whether the researcher has made

a correct decision or has made a Type 1 or Type 2 error. Explain why.

1. Dr. G rejects the null hypothesis although the independent variable had no

effect.

2. Dr. R rejects the null hypothesis when it is false.

3. Although the independent variable had an effect, Dr. E does not reject the

null hypothesis

1. Dr. G rejects the null hypothesis although the independent variable had no effect. This

problem would be a type I error because there is no proof that shows that the null hypothesis was

false. A Type I error is made when the null hypothesis is true and is rejected. Dr. G rejected the

null hypothesis without completely knowing if the null hypothesis is false.

2. Dr. R rejects the null hypothesis when it is false. This would be a corrected decision. Again,

we reject the null hypothesis if it is false and that is what happened in this scenario.

3. Although the independent variable had an effect, Dr. E does not reject the null hypothesis.

This is a Type II error. A type II error happens as a type of false positive. Meaning, that Dr. E

failed to reject a null hypothesis that is actually false.

Explain the value of reversal designs (ABA designs) in single-case

research.

This type of research can be extremely helpful. For example, reversal designs in single-case

research allows researchers to obtain repeated measures. In this type of design, the researcher

tries to verify the effects of the independent variable by "reversing" the roles. This causes more

consistency within the study and is accurately measured under controlled conditions. This reduces types or errors as well.