Contents
How do you use the Spearman-Brown prophecy formula?
Spearman-Brown Formula
- rkk = reliability of a test “k” times as long as the original test,
- r11 = reliability of the original test(e.g. Cronbach’s Alpha),
- k = factor by which the length of the test is changed. To find k, divide the number of items on the original test by the number of items on the new test.
What is Spearman-Brown correction?
The Spearman-Brown correction is a specific form of the Spearman-Brown predicted reliability formula. Suppose we have a test with reliability ρ. The reliability ρ′ of the test replicated n times is given by the formula. When n = 2, we have the Spearman-Brown correction for halves of equal length.
What is acceptable Spearman-Brown coefficient?
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 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 is Spearman-Brown formula used for?
Reliability coefficients that are based on classical test theory can be expressed as intraclass correlation coefficients (ICCs), such as Cronbach’s alpha. The Spearman-Brown prophecy formula (SB formula) is used to calculate the reliability when the number of items in a questionnaire is changed.
What is Spearman-Brown used for?
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 is the Spearman-Brown prophecy formula used?
Reliability coefficients that are based on classical test theory can be expressed as intraclass correlation coefficients (ICCs), such as Cronbach’s alpha. The Spearman-Brown prophecy formula (SB formula) is used to calculate the reliability when the number of items in a questionnaire is changed.
How to calculate Spearman-Brown predicted reliability for items?
SB_PRED(m, rho, n) = Spearman-Brown predicted reliability based on m items when Spearman-Brown for n items is rho. SB_SIZE(rho1, rho, n) = the number of items necessary to bring the Spearman-Brown predicted reliability up (or down) to rho1 from n items with Spearman-Brown of rho SB_PRED (24, .5, 12) = .667
How is the Spearman-Brown formula used in psychometric analytics?
The Spearman-Brown Formula To adjust for this, psychometricians use the Spearman-Brown prophecy formula. It takes the split half correlation as input and converts it to an estimate of the equivalent level of reliability for the full-length test. While this might sound complex, the actual formula is quite simple.
Is the Spearman-Brown formula based on assumptions?
It is based on the idea that split-half reliability has better assumptions than coefficient alpha but only estimates reliability for a half-length test, so you need to implement a correction that steps it up to a true estimate for a full-length test. Looking for software to help you analyze reliability?