Chapter 8, Problem 1RQE

Summary Introduction

Introduction:

Internal invalidity happens when conclusions drawn from an experiment do not accurately indicate the conditions of the experiment. History can be a factor if an event occurs during the experiment that could bias responses. A subject may become bored during an experiment, influencing responses later in the process, a factor called maturation. Instrumentation refers to changes in the way the dependent variable is measured, which throws off results because the later ones cannot be compared to the previous ones. If the control group begins resent what they view as unequal treatment, they may become demoralized and not respond the same way they otherwise might.

Explanation of Solution

Answer and explanation:

(This question requires a subjective answer, this is an example.)

If the conclusions of an experiment do not reflect the way the experiment was conducted, the result is internal invalidity. This can happen in many different ways. History can be a factor, for example, if the researchers are studying attitudes toward gun control laws, and a mass shooting occurs, the attitudes of the subjects may change due to the event. Another factor is maturation, in which the subjects may become bored over the course of the experiment. For example, participants may be initially excited to be involved in a study about skateboarding injuries, but become disinterested if the study takes a long time to gather enough data, or feels repetitive. Instrumentation becomes a factor in experiments with pretests and posttests if the latter is different from the former. If a teacher wanted to measure how much his students learned in class and gave a pretest to gauge how much knowledge the students had at the beginning of the course, the test at the end of the course must be the same in order to compare the variables in a valid manner. If the teacher changes the test, even by correcting misleading questions, the measure becomes invalid. If subjects realize they are in the control group in an experiment, they may become demoralized, which could change how they respond going forward. For example, if an experimenter does not use double-blind methods and accidentally tips off the control group that they are getting a placebo, that revelation may cause subjects in that group to become resentful. If a subject resents the conditions of the experiment, he or she may assume the independent variable will have no effect on them, causing a bias in their responses.