Factors that affect reliability coefficients

Full Answer Section

   

• Test-Retest Reliability:This reflects the consistency of scores when the same test is administered to the same individuals on separate occasions, assuming no significant changes in the underlying construct. Factors like fatigue, learning effects, or environmental differences can impact test-retest reliability, affecting the coefficient.

2. Test-Retest Method:

This method involves administering the same test to the same participants at two different time points. The correlation between the scores at each time point indicates the test-retest reliability. Suitable studies: This method works well for stable constructs (e.g., personality traits) where minimal change between testing periods is expected. Best Use:

• When internal consistency is difficult to assess (e.g., performance tests).
• When longitudinal data is needed to gauge measurement stability over time.

Limitations:

• Practice effects can inflate scores on the second administration.
• External factors like participant mood or environment can influence results.
• Not suitable for rapidly changing constructs (e.g., mood states).

3. Relationship between Reliability and Validity:

Validity: The degree to which a measurement tool actually measures the intended construct. Relationship: Reliability is a necessary but not sufficient condition for validity. A reliable test consistently measures something, but it doesn't guarantee it measures what it's supposed to. Imagine a scale that always reads 5 pounds heavier than your actual weight – it's reliable (consistent), but not valid (doesn't measure weight accurately).

4. Criterion-Related Validation:

This method compares scores on the test with an established measure known to reflect the same construct (the criterion). Steps include:

1. Define the construct:Clearly specify what the test measures.
2. Select a criterion:Choose a reliable and valid measure of the same construct.
3. Administer both measures:Give the test and the criterion measure to the same participants.
4. Analyze the correlation:Calculate the correlation between the test scores and criterion scores.
5. Interpret the results:A high correlation indicates the test is valid.
6. Standard Error of Measurement (SEM):

This statistic estimates the average amount of error associated with an individual score on a test. A smaller SEM signifies greater precision in measurement. Confidence Intervals (CIs): These intervals estimate the range of scores within which the true score of an individual is likely to fall, with a certain level of confidence (e.g., 95%). A smaller SEM leads to narrower CIs, indicating greater confidence in the estimated range.

6. Restriction of Range:

This occurs when the sample population tested does not represent the full range of potential scores on the construct. For example, testing only high-performing students might restrict the range of scores and underestimate the true variability of the test. Effect on Validity Coefficient: Restriction of range can artificially inflate the validity coefficient, making it appear higher than it actually is. This is because the limited range reduces the possibility of finding unrelated scores, artificially boosting the correlation between the test and the criterion.  

Sample Answer

   

. Factors Affecting Reliability Coefficients:

Reliability coefficient: A statistical measure indicating the consistency or precision of a measurement tool. A value closer to 1 signifies higher reliability, meaning the instrument produces similar results on repeated administrations. Two factors affect reliability:

• Internal Consistency: This refers to the extent to which items within a single assessment measure the same construct. Factors like unclear wording, ambiguity, or extraneous questions can decrease internal consistency, lowering the reliability coefficient.