Podcast
Questions and Answers
Which of the following is NOT a factor affecting internal consistency reliability?
Which of the following is NOT a factor affecting internal consistency reliability?
What is the most common method of estimating reliability?
What is the most common method of estimating reliability?
What is the relationship between the length of a test and its internal consistency reliability?
What is the relationship between the length of a test and its internal consistency reliability?
Internal consistency is a better alternative to alternative forms and test-retest procedures.
Internal consistency is a better alternative to alternative forms and test-retest procedures.
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The internal consistency reliability procedure requires respondents to complete one form of a test on one occasion
The internal consistency reliability procedure requires respondents to complete one form of a test on one occasion
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What does the Spearman-Brown formula adjust for in the internal consistency reliability estimate of a test?
What does the Spearman-Brown formula adjust for in the internal consistency reliability estimate of a test?
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Which of the following is a limitation of the split-half reliability approach?
Which of the following is a limitation of the split-half reliability approach?
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What is the major advantage of the split-half reliability approach over the alternative forms reliability method?
What is the major advantage of the split-half reliability approach over the alternative forms reliability method?
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What is the Spearman-Brown Formula used for?
What is the Spearman-Brown Formula used for?
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Is the Spearman-Brown Formula useful for data that is standardized (t-scores & z-scores)?
Is the Spearman-Brown Formula useful for data that is standardized (t-scores & z-scores)?
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Which of the following best describes Cronbach's alpha?
Which of the following best describes Cronbach's alpha?
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Why is it important for an instrument to have a high level of covariance among its items?
Why is it important for an instrument to have a high level of covariance among its items?
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Which assumption is NOT assumed for Cronbach's alpha
Which assumption is NOT assumed for Cronbach's alpha
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Which of the following represents the numerator in Cronbach's alpha formula?
Which of the following represents the numerator in Cronbach's alpha formula?
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What does the denominator in Cronbach's alpha formula represent?
What does the denominator in Cronbach's alpha formula represent?
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The standardised coefficient alpha is used for raw scores
The standardised coefficient alpha is used for raw scores
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What does Cronbach's alpha formula represent at the theoretical level?
What does Cronbach's alpha formula represent at the theoretical level?
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The standardised coefficient alpha should have similar variances and be similar in magnitude to the coefficient alpha
The standardised coefficient alpha should have similar variances and be similar in magnitude to the coefficient alpha
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What is the main limitation of Cronbach's alpha when it comes to positively correlated error terms between two items within a test?
What is the main limitation of Cronbach's alpha when it comes to positively correlated error terms between two items within a test?
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Which formula is mostly of historical interest for estimating internal consistency reliability associated with composite scores based on dichotomously scored items?
Which formula is mostly of historical interest for estimating internal consistency reliability associated with composite scores based on dichotomously scored items?
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What is the Kuder-Richardson formula used for?
What is the Kuder-Richardson formula used for?
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If the assumption of essential tau-equivalence is not satisfied, then Cronbach’s alpha will tend to:
If the assumption of essential tau-equivalence is not satisfied, then Cronbach’s alpha will tend to:
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With a reasonable amount of items (10 or more) Cronbach’s alpha will underestimate reliability by:
With a reasonable amount of items (10 or more) Cronbach’s alpha will underestimate reliability by:
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Which formula is a better alternative to the Kuder-Richardson formula for estimating internal consistency reliability for non-dichotomously scored items?
Which formula is a better alternative to the Kuder-Richardson formula for estimating internal consistency reliability for non-dichotomously scored items?
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A smaller number of items (say, 3 to 6 items) will cause the degree of the Cronbach's alpha underestimation to lessen
A smaller number of items (say, 3 to 6 items) will cause the degree of the Cronbach's alpha underestimation to lessen
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In practice, violating the assumption of non-correlated error terms can result in Cronbach’s alpha to:
In practice, violating the assumption of non-correlated error terms can result in Cronbach’s alpha to:
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What is the main factor to consider when deciding whether to add an item to a test to increase its reliability?
What is the main factor to consider when deciding whether to add an item to a test to increase its reliability?
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What is the textbook's recommendation for added items to a test in order to increase Cronbach's alpha?
What is the textbook's recommendation for added items to a test in order to increase Cronbach's alpha?
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What is the purpose of adding an item to a test according to the text?
What is the purpose of adding an item to a test according to the text?
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Study Notes
Factors Affecting Internal Consistency Reliability
- The length of a test and its internal consistency reliability are positively related.
- Internal consistency is not affected by the time of administration, respondents' characteristics, or the test's content.
Estimating Reliability
- The most common method of estimating reliability is internal consistency reliability.
- Internal consistency is a better alternative to alternative forms and test-retest procedures.
Internal Consistency Reliability Procedure
- The internal consistency reliability procedure requires respondents to complete one form of a test on one occasion.
Spearman-Brown Formula
- The Spearman-Brown formula adjusts for the length of a test in the internal consistency reliability estimate.
- The formula is used to estimate the reliability of a test based on its current length and the desired length.
- The formula is not useful for data that is standardized (t-scores & z-scores).
Split-Half Reliability Approach
- The major advantage of the split-half reliability approach is that it can be used when there is no alternative form of the test.
- A limitation of the split-half reliability approach is that it may not be suitable for tests with a small number of items.
Cronbach's Alpha
- Cronbach's alpha is a measure of internal consistency reliability.
- It is important for an instrument to have a high level of covariance among its items to ensure reliability.
- Cronbach's alpha formula represents the average correlation among all possible split-half combinations of items.
- The numerator in Cronbach's alpha formula represents the sum of the covariances between items.
- The denominator in Cronbach's alpha formula represents the variance of the total score.
- The standardised coefficient alpha is used for raw scores and should have similar variances and be similar in magnitude to the coefficient alpha.
- At the theoretical level, Cronbach's alpha formula represents the proportion of the total variance that is due to the true score.
Limitations of Cronbach's Alpha
- The main limitation of Cronbach's alpha is that it can be affected by positively correlated error terms between two items within a test.
- If the assumption of essential tau-equivalence is not satisfied, then Cronbach’s alpha will tend to underestimate reliability.
- With a reasonable amount of items (10 or more), Cronbach’s alpha will underestimate reliability by 5-10%.
- A smaller number of items (say, 3 to 6 items) will cause the degree of the Cronbach's alpha underestimation to lessen.
- In practice, violating the assumption of non-correlated error terms can result in Cronbach’s alpha to overestimate reliability.
Kuder-Richardson Formula
- The Kuder-Richardson formula is of historical interest for estimating internal consistency reliability associated with composite scores based on dichotomously scored items.
- The formula is used for estimating internal consistency reliability for dichotomously scored items.
Adding Items to a Test
- The main factor to consider when deciding whether to add an item to a test is the item's correlation with the total score.
- The textbook's recommendation for adding items to a test is to add items that are highly correlated with the total score.
- The purpose of adding an item to a test is to increase its reliability.
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Description
Test your knowledge on internal-consistency reliability, the most common method of estimating reliability. Learn about its practical alternative to the alternative forms procedure and the test-retest procedure. Explore how the internal consistency reliability procedure treats different items within the same test as different forms.
