Methods Toward a Science of Behavior and Experience 10th International Edition by William J. Ray – Test Bank
Chapter 7 – Testing the Hypothesis: A Conceptual Introduction
The Context of Experimentation: An Example
Types of Variation
Systematic Variation Due to the Independent Variable
Systematic Variation Due to Confounds
Statistical Hypothesis Testing
Threats to Internal Validity
Diffusion or Imitation of Treatments
Interpreting the outcome of an experiment requires making decisions about the source of any variance. These sources may include chance variance, systematic variation due to the independent variable, and systematic variation due to confounds. Each source of variance has implications for the probability of making Type I and Type II errors. Variance is analyzed using the F ratio, which uses within-groups variance (chance or error variance) and between-groups variance.
There are several threats to internal validity. They include history, maturation, testing, instrumentation, statistical regression, selection, mortality, selection-maturation interaction, and diffusion.
1. Evaluation of a research hypothesis is a complex process. Identify three important questions you should consider in your evaluation.
2. What three resources do we use when looking for unknown factors that may be responsible for the experimental outcome?
3. Why is chance always involved in our sampling and observations of the world?
4. Why do we never state that the independent variable absolutely caused the effect on the dependent variable?
5. Why is it essential that the initial phase of any experiment be a statistical decision process?
6. What is the role of confounds in the research process?
7. Why do we try to eliminate sources of uncontrolled variance that operate in a systematic manner?
8. Why do scientists argue that the heart of experimentation lies in ruling out alternative explanations?
9. What is the F-ratio? How can it be explained in terms of within-groups variance and between-groups variance? How does this relate to the treatment effect and error variance?
10. What is the relationship between a calculated F-value that is close to 1 and the null hypothesis? What is the general rule regarding the value of the F-ratio and the certainty of differences between groups that are not caused by chance alone?