If an experiment is set up to severely test whether influence X really does affect outcome Y then it needs to be clear any systematic changes in Y are wholly due to the change in X. This is the issue of internal validity.

Internal validity

Refers to the extent to which research findings would have relevance and application in the real world.

Ecological Validity

For all experiments, there is always compromise across all aspects of validity, at the very least ecological because in order to achieve experimental control, some aspects of the real world need to be constrained. Depending on the complexity of the idea being tested in the experiment, different compromises need to be made. 

Validity as a whole

Face validity is a subjective assessment of how well a measurement tool appears to measure the concept it is intended to, based on a surface-level inspection. It considers whether the measure seems appropriate and relevant for its stated purpose at first glance.

Face Validity

Discriminant validity is the extent to which scores on a measure are not strongly correlated with measures of conceptually distinct variables. Providing evidence of low correlations between differing constructs—such as self-esteem and mood—is crucial to demonstrate that the new measure is uniquely capturing the intended trait rather than inadvertently measuring a different psychological state.

Discriminant Validity

Content validity refers to the extent to which a measure adequately covers all aspects of the theoretical construct it is designed to assess. In psychological measurement, researchers often rely on multiple-item measures to achieve content validity because a single item rarely captures the full complexity of a construct comprehensively.

Content Validity

Criterion validity involves evaluating how effectively a measure aligns with expectations by correlating it with other relevant variables. Researchers assess this by analyzing the correlations among multiple measures of the same psychological construct, or by verifying expected relationships with measures of conceptually distinct constructs. Additionally, a successful experimental manipulation inherently provides evidence for criterion validity. For example, if an experiment manipulates participants' moods by instructing them to think positive versus negative thoughts, and the subsequent mood measure reveals a distinct difference between the two groups, this simultaneously demonstrates that the manipulation worked and that the measurement tool was valid.

Criterion Validity

External validity refers to the ability to generalize the results of a study beyond the specific people and situations that were actually investigated.

External Validity

Construct validity assesses the quality of a study's experimental manipulations and how accurately those procedures operationalize the core conceptual research question. A research design demonstrates high construct validity when the variables are manipulated in a way that clearly isolates the specific phenomenon of interest. This validity depends heavily on the nuances of the experimental design, such as the number of conditions. For example, in Darley and Latané’s study on bystander intervention, testing only two conditions (one versus two other students) might merely demonstrate general social inhibition rather than the specific diffusion of responsibility, resulting in lower construct validity; expanding to multiple conditions helps clarify the phenomenon, though adding too many conditions may eventually plateau without adding further insight.

Construct Validity

In psychological research, what is the primary purpose of evaluating distinct forms of measurement validity, such as face, content, and criterion validity?

Validity is often divided into several distinct types, which represent different kinds of evidence researchers use to judge a measure's accuracy. Beyond reliability, researchers evaluate evidence through various forms of validity, such as face validity, content validity, and criterion validity, to ensure the measurement method truly captures the intended construct.

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Experimental designs are written up in papers as objective descriptions of a state of affairs and the complex processes that led to that particular experiment are glossed over. In particular, the fact that an experimental design may have been iterated on paper, tested in a pilot or even failed entirely and iterated further may only merit the briefest of mentions, if any.


Experimental design

Validity in research refers to the degree to which an instrument or tool correctly measures the concept it is intended to assess. It addresses the accuracy of the measurement, ensuring that the data collected is a true representation of the phenomenon under study.

Validity in Research

Spielman, R. M., Jenkins, W. J., & Lovett, M. D. (2020, April 22). Psychology (2nd ed.). OpenStax. https://openstax.org/books/psychology-2e/pages/1-introduction

OpenStax Psychology (2nd ed.) Textbook

https://kpu.pressbooks.pub/psychmethods4e/

KPU Research Methods in Psychology - 4th American Edition

The starting point of an experiment as a severe test is to set up a situation that tests an idea and that idea must be causal: one thing should influence another. In HCI-style experiments, this is also expressed as seeing the effect of the independent variable on the dependent variable. 


Starting point of an experiment

Types of Validity

A key distinction in research methodology is that a measure can be reliable, meaning it consistently produces the same result, without being valid, as it may not accurately measure the intended concept. Conversely, any measure that is considered valid must inherently be reliable. Therefore, while validity necessitates reliability, reliability alone does not guarantee validity.

Relationship Between Reliability and Validity

A researcher wants to measure the overall 'physical fitness' of adults. To do this, they measure how many push-ups each participant can complete in one minute. What is the most significant potential flaw in this measurement approach?

When critically evaluating psychology experiments, researchers focus on four major validities to assess whether a study is sound and accurate: internal validity, external validity, construct validity, and statistical validity. Each of these four frameworks addresses a different dimension of the experiment's methodology, from how well it establishes causality and generalizes to the real world, to the quality of its manipulations and the appropriateness of its statistical conclusions.

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