Personality

Reliability: Refers to the consistency of a measure; high reliability indicates less error in measurement. This means that the measure effectively ‘squeezes out’ variability caused by errors.
Validity: A measure's ability to accurately assess what it claims to measure. It is often seen as the credibility or meaningfulness of the measure.
- Commonly viewed as a 'pun' or 'span' of measure or test. The perception of validity by laypersons is less significant than the actual validity assessed by psychological standards.

Definition: Content validity refers to how well the items on a test represent the construct being measured. It examines whether the content covers all manifestations of the construct broadly enough.
Example: For an anxiety test, it would be inappropriate to create questions solely focused on one symptom (e.g., sweating). Instead, a wide array of manifestations of anxiety should be covered such as:
- Sweating
- Dry mouth
- Feeling jittery
- Feeling apprehensive
- Feeling nervous
- Feeling jumpy
- Feeling worried
Importance: Broad sampling of the construct ensures the test measures the intended concept comprehensively, contributing to a valid measure.

Content validity is assessed subjectively but should be backed by thorough research and expert opinions.
- Collaboration with subject matter experts can help determine if items adequately sample the domain.
- Inadequate attention to content validity can lead to poor internal consistency or correlation with other related constructs.

Definition: The extent to which test scores correlate with an external criterion, which may be a behavior, skill, or aptitude. There are two important types of criterion validity:
- Concurrent Validity: Correlation assessed at the same time as performance on the criterion.
- Predictive Validity: Correlation assessed at a later time, where scores on the test predict future behavior or outcomes.

There may be ethical concerns with using certain criteria (e.g., throwing someone in a pool to test swimming ability).
Establishing valid observable criteria can be complex, especially in psychology where many constructs (e.g., anxiety) are not easily quantifiable.
- Observations or assessments that correlate with constructs such as avoidance behaviors or anxiety attacks can be more elusive.

Definition: The extent to which a test truly measures the theoretical construct it intends to measure. Established through a combination of methodologies.
Key contributions are summarized as follows:
- Item Correlation: Items measuring the same construct should correlate with each other. High internal consistency is desired, implying the items represent the same concept.
- Manipulations: Ability to manipulate variables affecting the construct should produce predictable results. E.g., in anxiety tests, proving that treatment reduces symptoms validates the construct being measured.
- Process: Understanding how the construct relates to other constructs, suggesting a sequence (A -> B -> C) is necessary.
- Group Differences: Testing differences in behavior between groups (e.g., high, medium, low scores on an anxiety scale) can validate if the test is measuring what it is supposed to.
- Factor Analysis: A data reduction technique identifying underlying structure among responses, ensuring that measures relate logically to the constructs.
- Correlation Analysis: Establishing convergent and divergent patterns. High scores on the anxiety test should correlate positively with other related measures and show little to no correlation with unrelated measures.

Significance: Validity ensures that psychological assessments accurately contribute to scientific research. If measures are invalid, results may reflect random noise rather than meaningful data.
Ongoing collection of data is necessary for affirming construct validity over time.

Caution is required in correlating results with external behaviors. The ability to predict outcomes based on test scores is crucial, affecting decisions in clinical and applied settings.

Understanding and implementing reliability, content validity, criterion validity, and construct validity are crucial components in the development and evaluation of psychological measures. Ensuring these measures align with theoretical constructs contributes to successful outcomes in psychological testing and research.