Kuder-Richardson #21 Formula for estimate test reliability

[pkaraffa]

Good Morning!

I am trying to figure out how to adapt the Kruder-Richardson Formula
#21 to excel. First of all this is not a homework assignment.
Secondly, I appologize for linking a file but I could not get the
fonts for the formula right. What the formla does is to estimate test
reliability. I can figure it out long hand but would greatly
appreciate it in excel thanks in advance.

R=( k) (1- X(k-X))
----- -----------
k-1 kS

where
R= test reliability
k = number of items on the test
X = mean of raw scores from the total test
S = vfariance from the raw scores of the total test

Suppose we had a 50 item test and the mean score was 43 and the
variance was 25.0. We would have

R= (50) (1- 43(50 - 43))
----- --------------
50-1 (50)(25)

R = (1.02) (1- 301)
----
1250

R = (1.02) (0.76) = 0.78


Thank you in advance.

http://www.savefile.com/projects/808560688

 

[JE McGimpsey]

One way:

=(k/(k-1)) * (1 - (X*(k-X))/(k*S))

You can either name your cells k, X, and S, or replace the k,X,S in the
formula with cell references.

 

[Bernd P]

Hello,

If you google for "Kuder-Richardson 21 Formula excel" then you will
find
http://www.gifted.uconn.edu/siegle/research/Instrument Reliability and Validity/Reliability.htm
which links to a [IMHO] nice sample spreadsheet
http://www.gifted.uconn.edu/siegle/...ility and Validity/reliabilitycalculator2.xls

Some things are easier copied than re-invented.

Regards,
Bernd

 

[JE McGimpsey]

A caveat -

There are tens of thousands of workbooks out there that can be copied. A
significant fraction of them, including ones posted by academics, have
errors or have poor boundary event error checking.

Validating someone else's worksheet for a simple calculation like this
can often be *more* difficult than building from scratch...

 

[pkaraffa]

A caveat -

There are tens of thousands of workbooks out there that can be copied. A
significant fraction of them, including ones posted by academics, have
errors or have poor boundary event error checking.

Validating someone else's worksheet for a simple calculation like this
can often be *more* difficult than building from scratch...



- Show quoted text -

Thank you both!