Why is Spearman-Brown formula for split-half method?

Why is Spearman-Brown formula for split-half method?

The reasoning is that if both halves of the test measure the same construct at a similar level of precision and difficulty, then scores on one half should correlate highly with scores on the other half. More information on split-half is found here.

What is an acceptable Spearman-Brown?

Internal consistency was measured using a Spearman-Brown coefficient with values between . 70 to . 90 considered acceptable [48, 49] and Cronbach alpha with a range of . 70 to . 95 considered acceptable [29,46].

What does the Spearman-Brown correction do?

The Spearman-Brown prophecy formula provides a rough estimate of how much the reliability of test scores would increase or decrease if the number of observations or items in a measurement instrument were increased or decreased.

How do you split a half correlation?


  1. Administer the test to a large group students (ideally, over about 30).
  2. Randomly divide the test questions into two parts. For example, separate even questions from odd questions.
  3. Score each half of the test for each student.
  4. Find the correlation coefficient for the two halves.

What is the rationale behind the Spearman-Brown prophecy formula?

What is the rationale behind the Spearman-Brown prophecy formula? Longer tests are more reliable than shorter tests. What is the reliability of a test if the observed score standard deviation is 10, and the true score and the standard error of measurement are 3?

Which formula is used in split-half method of reliability?

Therefore, the split-half reliability estimation, which was calculated between the scores of the two halves of the test, involves an additional step in which the correlation is corrected for test length using the Spearman-Brown prophecy formula rpredicted=Nr1+(N−1)r r predicted = N r 1 + ( N − 1 ) r , where r is the …

What is Spearman-Brown formula for reliability?

In the formula(4) r Spearman -Brown = n r 1 + ( n − 1 ) r n is the factor by which the number of items will be multiplied, and r is the reliability (internal consistency) of the questionnaire.

What results come out in construct validity?

Construct validity should demonstrate that scores on a particular test do predict the theoretical trait it says it does. Convergent construct validity tests the relationship between the construct and a similar measure; this shows that constructs which are meant to be related are related.

What is the formula for split-half method?

SPLITHALF(R1, type) = split-half measure for the scores in the first half of the items in R1 vs. the second half of the items if type = 0 and the odd items in R1 vs. the even items if type = 1.

What is split-half coefficient?

The Guttman Split-half coefficient is computed using the formula for Cronbach’s alpha for two items, inserting the covariance between the item sums of two groups and the average of the variances of the group sums. Notice that different splits of the items will produce different estimates of the reliability coefficient.

How is internal consistency reliability measured?

Internal consistency is usually measured with Cronbach’s alpha, a statistic calculated from the pairwise correlations between items. Internal consistency ranges between negative infinity and one. Coefficient alpha will be negative whenever there is greater within-subject variability than between-subject variability.

Why is face validity important?

In sum, having face-valid assessments will likely lead to higher perceptions of fairness and more favorable perceptions towards the organization. Additionally, applicants who are rejected will be less likely to perceive the hiring process as biased if the assessments have high face validity.

When do you use the Spearman Brown formula?

When n = 2, we have the Spearman-Brown correction for halves of equal length. Another way to view the Spearman-Brown formula is as follows: suppose that the reliability for a test with m items is ρ, then a test with mn items will have reliability ρ′.

When did Spearman and Brown criticize each other?

Spearman (1910) criticized Brown (1910), but Brown (1910) criticized only Spearman (1904). Fourth, it is the APA style to list the authors in alphabetical order. This formula is commonly used by psychometricians to predict the reliability of a test after changing the test length.

Who is better William Brown or William Spearman?

William Brown received his Ph.D. under Pearson’s guidance. An important part of Brown’s doctoral dissertation was devoted to criticizing Spearman’ work. Spearman appears first in this formula before Brown because he is a more prestigious scholar than Brown.

Which is better Spearman 1910 or brown 1910?

Second, the formal derivation of Brown (1910) is more concise and elegant than that of Spearman (1910). Third, it is likely that Brown (1910) was written before Spearman (1910). Brown (1910) is based on his doctoral dissertation, which was already available at the time of publication.