Threats to Internal Validity and Null Effects

Flashcards covering threats to internal validity, methods to prevent them, and reasons for null effects, including variance within and between groups.

What are three common threats to internal validity?

Design confounds, selection effects, and order effects.

What is history as a threat to internal validity?

A historical or external event that affects most members of the treatment group at the same time as the treatment, making it unclear if the outcome is due to the treatment or the external event.

What is maturation as a threat to internal validity?

A change in participants over time due to natural development or spontaneous improvement/deterioration, rather than the intended intervention.

What is regression as a threat to internal validity?

The statistical phenomenon where extreme scores at one measurement tend to be closer to the average at a subsequent measurement.

What is attrition as a threat to internal validity?

When participants drop out of a study before it is completed, especially if there's a systematic reason for specific types of participants to drop out more than others.

What is testing as a threat to internal validity?

A change in participants' scores on a second administration of a test due to having taken the test before (e.g., practice effects or fatigue effects).

What is instrumentation as a threat to internal validity?

When the measurement instrument or observation method changes over time, affecting how the outcomes are recorded.

What is observer bias as a threat to internal validity?

When researchers' expectations influence their interpretation of the results or their behavior toward participants.

What are demand characteristics as a threat to internal validity?

When participants guess what the study is supposed to be about and change their behavior in the expected direction.

What are placebo effects as a threat to internal validity?

When people improve simply because they believe they are receiving an effective treatment, not because of the specific active ingredient of the treatment.

How can comparison groups help prevent threats to internal validity in experiments?

Comparison groups provide a baseline against which to evaluate the effect of the treatment, helping control for history, maturation, and other threats that affect both groups similarly.

How can double-blind studies help prevent threats to internal validity in experiments?

Double-blind studies prevent both observer bias and demand characteristics by ensuring neither the participants nor the researchers know who is in the treatment group and who is in the control group.

What other design choices can help researchers avoid many threats to internal validity?

Other design considerations such as comparison groups and double-blind studies can help researchers avoid many threats to internal validity.

Define comparison groups in the context of preventing threats to internal validity.

Comparison groups are groups in an experiment that do not receive the treatment or receive a different level of treatment, used to observe natural changes or effects of confounding variables.

Define double-blind studies in the context of preventing threats to internal validity.

Double-blind studies are experiments in which neither the participants nor the researchers who interact with the participants know who is receiving the treatment and who is receiving the control.

What are some other design choices that can help researchers avoid threats to internal validity?

Comparison groups, double-blind studies, and other well-planned design considerations can help researchers avoid many threats to internal validity.

What are three reasons why a study might result in null effects?

Not enough variance between groups, too much variance within groups, or a true null effect.

What are two ways a study might show inadequate variance between groups, and how can researchers identify such problems?

A study might show inadequate variance between groups due to weak manipulations or insensitive measures. Researchers can identify these problems by checking manipulation checks for weak manipulations and using reliable and valid measures for insensitive measures.

Why can large within-groups variance can obscure a between-groups difference?

Large within-groups variance can obscure a between-groups difference because the variability among individuals within each group is so high that it makes it difficult to detect a true difference between the averages of the groups.

What are three causes of within-group variance?

Measurement error, individual differences, and situation noise.

What is measurement error as a cause of within-group variance, and how might it be reduced?

Measurement error is the difference between a true score and a measured score due to inaccuracies in the measurement tool or process. It can be reduced by using reliable and precise measurement tools.

What are individual differences as a cause of within-group variance, and how might they be reduced?

Individual differences refer to the unique characteristics or traits of each participant that contribute variability to the data. They can be reduced through study designs like within-subjects designs or by increasing sample size.

What is situation noise as a cause of within-group variance, and how might it be reduced?

Situation noise refers to any external distractions or uncalibrated factors in the experimental setting that can increase variability within groups. It can be reduced by maintaining a highly controlled experimental environment and standardizing procedures.