Statistical Sciences 2035 Study Guide - Quiz Guide: Partial Correlation, Sampling Distribution, Mathematically Correct
7 Oct 2018
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Power of a correlation coefficient study
Approximate number of participants needed for 80% power for a study, using the
correlation coefficient (r) for testing a hypothesis at the .05 significance level:
How to report results of a Pearson correlation test:
A set of Pearson correlations were computed to determine if there was any significant
relationship between starting and current salary. The correlation between both is +.735;
this is significant at the .01 level. The null hypothesis can be rejected. Starting salary
appears to provide a moderate guide to current salary as it predicts around 54%
(0.7352*100) of current salary level. The remainder of the unexplained variance may
involve inter alia qualifications/skills developed over the time period and differential
opportunities for promotion.
Spearman’s rank order correlation (rho)
Rank order correlation follows the same principles as outlined earlier and ranges from
+1 to –1. While rho is only suitable for ranked (or ordinal) data, interval data can also
be used provided it is first ranked. It is typically used when there are only a few cases
(or subjects) involved, designated as ‘rho’, and it is based on the differences in ranks
between each of the pairs of ranks. However, rho will always provide a lower estimate
of correlation than r because the data is degraded.
How to report results:
A Spearman rho of +.10 was recorded between current salary and sales performance at
the end of period three. This was not statistically significant and therefore the null
hypothesis must be retained. Given that there is no statistically significant relationship,
sales performance is no guide to current salary. The relationship is so low as to be
random, and other variables not measured in this study must have a greater influence in
determining salary level.
Document Summary
Approximate number of participants needed for 80% power for a study, using the correlation coefficient (r) for testing a hypothesis at the . 05 significance level: How to report results of a pearson correlation test: A set of pearson correlations were computed to determine if there was any significant relationship between starting and current salary. The correlation between both is +. 735; this is significant at the . 01 level. Starting salary appears to provide a moderate guide to current salary as it predicts around 54% (0. 7352*100) of current salary level. The remainder of the unexplained variance may involve inter alia qualifications/skills developed over the time period and differential opportunities for promotion. Rank order correlation follows the same principles as outlined earlier and ranges from. While rho is only suitable for ranked (or ordinal) data, interval data can also (cid:523)or subjects(cid:524) involved, designated as (cid:494)rho(cid:495), and it is based on the differences in ranks be used provided it is first ranked.
