Correlation analysis, Upper 95% CI and Lower 95% CI of Spearman's rho
I have a question with regard to Correlation analysis, especially the output of Upper 95% CI and Lower 95% CI of Spearman's rho in the Correlation Table.
In some of my analyses, I only had to select „Additional option“ „Confidence interval“ and then the Upper 95% CI and the Lower 95% CI of Spearman's rho were shown.
In other analyses, when I selected the „Additional Option“ „Confidence interval“, the Upper 95% CI and the Lower 95% CI of Spearman's rho were not shown. I had to additionally select „Confidence Intervals from … bootstraps“ and then the Upper 95% CI and the Lower 95% CI of Spearman's rho were shown.
These are my questions:
With Pearson's r there is always immediately the Upper 95% CI and the Lower 95% CI. Why not with Spearman's rho?
What are the preconditions that cause JASP to handle analyses so differently?
Thank you very much in advance!
BTW:
When I de-select „Confidence Intervals from … bootstraps“, „slightly different“ values for the Upper 95% CI and the Lower 95% CI of Spearman's rho are shown (why?).
When I then de-select „Spearman's Rho“ all values related to Spearman's rho are not shown anymore (which is fine).
And when I then select „Spearman's Rho“ again, immediately all values related to Spearman's rho, including Upper 95% CI and Lower 95% CI of Spearman’s rho (the „slightly different“ previous values), are shown.
I left the JASP file without saving and started a second attempt to calculate the correlation. The behavior of the program was the same. The „slightly different“ values were identical to the „slightly different“ values from the first attempt to calculate the correlation.
It seems there is a bug?
I used JASP version 0.16.4
Comments
Dear B_S,
I suspect the computation of the CI interval for Spearman's rho requires the use of the bootstrap. Since the bootstrap is ticked off by default, no intervals are initially produced for Spearman's rho. It would be possible to have the bootstrap option ticked *on* by default, but this would mean that the intervals for Pearson's rho are by default based on the bootstrap (and hence will yield slightly different results every time the analysis is run). So a different solution is needed. Perhaps we could produce analytic approximations for the CI of Spearman's rho, but I am not sure these exist. I'll ask our expert. BTW, I think we ought to continue this discussion on our GitHub page, because it relates to a bug or feature request.
Cheers,
E.J.