Hi there,

I am calculating Difficulty with Rank-biserial correlation coefficients in a spreadsheet using the following formula:

rb = (2/n)*(Y1 - Y0)

where Yo and Y1 are the means on Y of those scoring 0 and 1 on the dichotomy, respectively.

This was sourced from Glass (1966) - Note on Rank Biserial Correlation

For one calculation I have arrived at an rb value of -1.5! This is obviously difficult to interpret. I'm hoping that somebody may be able to point out where I have gone wrong. Here is the data set:

Dichotomous variable: 1,1,1,0,1

Ordinal variable: 3,3,3,2,4 (Scale ranged from 0 to 4)

(0 and 2 are paired)

Can you see an obvious problem with what I am doing here?

Many thanks!

B

I am calculating Difficulty with Rank-biserial correlation coefficients in a spreadsheet using the following formula:

rb = (2/n)*(Y1 - Y0)

where Yo and Y1 are the means on Y of those scoring 0 and 1 on the dichotomy, respectively.

This was sourced from Glass (1966) - Note on Rank Biserial Correlation

For one calculation I have arrived at an rb value of -1.5! This is obviously difficult to interpret. I'm hoping that somebody may be able to point out where I have gone wrong. Here is the data set:

Dichotomous variable: 1,1,1,0,1

Ordinal variable: 3,3,3,2,4 (Scale ranged from 0 to 4)

(0 and 2 are paired)

Can you see an obvious problem with what I am doing here?

Many thanks!

B

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