Monthly Archives: March 2014

What does it mean to have a low R-squared ? A warning about misleading interpretation

A common argument we read everytime, everywhere. All with the same common mistake. It consists in squaring the correlation. For example : “Your brain-IQ correlation is r=0.40, so if you square it, that only amounts to a tiny 16% (r²=0.40*0.40=0.16) … Continue reading

Posted in Stats

Example of SIBTEST nonlinear regression correction applied to the logistic regression method of DIF detection (DeMars 2014, personal communication)

I am truly indebted to Christine E. DeMars (2009) who took the time to explicit the nasty formulas proposed by Jiang & Stout (1998). The use of regressed true score is preferable than using the mere observed score because a … Continue reading

Posted in Stats

How to remove the influence of confoundings on a (continuous) variable by way of linear regression

To see how it works, the best way is to show the process. If we need to remove the influence of, say, age and gender, on IQ, that would mean IQ would not correlate with either gender or age anymore. … Continue reading

Posted in Stats

Examining the Measurement Quality of Tests Containing Differentially Functioning Items: Do Biased Items Result in Poor Measurement?

Examining the Measurement Quality of Tests Containing Differentially Functioning Items: Do Biased Items Result in Poor Measurement? Mary Roznowski and Janet Reith (1999) This study investigated effects of retaining test items manifesting differential item functioning (DIF) on aspects of the … Continue reading

Posted in Stats

Skin Color, Verbal IQ, and Test of the Colorism Hypothesis in the GSS (syntax SPSS)

See related post here.

Posted in Stats, Softwares, Syntax | Tagged