3
$\begingroup$

The dichotomous variable I want to use for a point-biserial correlation has very unequal n's ($n_1=140$, $n_2=6$). Would this be breaking any rules? What would this mean for my results? Would it just limit the statistical power?

$\endgroup$
  • 1
    $\begingroup$ 1) No, it doesn't break formal assumptions for point-biserial r. 2) Yes it does limit statistical power. $\endgroup$ – ttnphns Mar 20 '13 at 21:21
1
$\begingroup$

I would first look at a scatterplot of the variables to see if they are linear before running an analysis. In addition, see Kraemer's 1980 paper,Robustness of the Distribution Theory of the Product Moment Correlation Coefficient, in which it is noted,

Robustness of normal test theory for correlation coefficients is at least asymptotically ensured for bivariate distributions satisfying a linearity and a homoscedasticity condition for the null theory and a further kurtosis condition for the nonnull theory. If any one of these conditions fail, it may be demonstrated that robustness may fail as well. (Abstract)

| cite | improve this answer | |
$\endgroup$
  • $\begingroup$ One variable is continuous. The dichotomous variable has the unequal group sizes. $\endgroup$ – axeman Mar 20 '13 at 19:04

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.