Point biserial correlation and sample size < 20

[Preethi Baligar]

Sir/Madams,

Im working on a sample of 60 students.

With a team size of 4 students per team, this comes down to 15 teams per group. 

some teams are all-boys teams while others are mixed gender teams. I call these as team-type( 0-all boys, 1 mixed gender) in SPSS. Team type is my dichotomous variable. Marks is a scale variable.

Now I need to test whether teamtype has any influence on the performance(scores) of the group. To do so, Im using a point-biserial correlation.

Issues that are bothering me

1. In the group there are only 4 mixed-gender teams and 11 all-boys teams.

2. I cannot collect any more data. 

3. Can I perform point-biserial correlation? how valid is this?  How can I justify this? 

Any pointers are truly appreciated! :) 

Regards,

Preethi Baligar

[Neeraj Kaushik]

Dear Preethi

Yes, you can use the Point Biserial Correlation.

A point-biserial correlation is used to measure the strength and direction of the association that exists between one continuous variable and one dichotomous variable 

(Source: https://statistics.laerd.com/spss-tutorials/point-biserial-correlation-using-spss-statistics.php

IMO, here you can also use t-test to check whether the 2 groups differ significantly or not?

Best wishes

Neeraj

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[Preethi Baligar]

Additionally,

Interpreting Point-biserial correlation is similarly to PMCC. I was wondering how to interpret this as interchanging the values of dichotomous variables will also reverse the sign of the correlation coefficient. 

I found the answer here..Source: DeCoster, J. (2004). Data Analysis in SPSS. Retrieved <month, day, and year you downloaded this file> from http://www.stat-help.com/notes.html

The interpretation of this variable is similar to the interpretation of the Pearson correlation. A positive correlation indicates that the group associated with the value of 1 has larger values than the group associated with the value of 0. A negative correlation indicates that the group associated with the value of 1 has smaller values than the group associated with 0

Thanking you,

Regards,

Preethi Baligar

Asst. Professor

Centre for Engineering Education Research

KLE Technological University,

Hubballi, India

On Tue, Aug 24, 2021 at 11:21 AM Preethi Baligar <pree...@kletech.ac.in> wrote:

Thank you Sir. 

Thanking you,

Regards,

Preethi Baligar

Asst. Professor

Centre for Engineering Education Research

KLE Technological University,

Hubballi, India

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[Preethi Baligar]

Thank you Sir. 

Thanking you,

Regards,

Preethi Baligar

Asst. Professor

Centre for Engineering Education Research

KLE Technological University,

Hubballi, India

On Tue, Aug 24, 2021 at 10:22 AM Neeraj Kaushik <kaushi...@gmail.com> wrote:

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[Neeraj Kaushik]

Yes, the interpretation is correct

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