Tim Lambert (deltoidblog AT gmail.com) is a computer scientist at the University of New South Wales.
Henry E. Schaffer said:
In articles various people say things like:
By the way, values of 0.48 and 0.45 are REALLY BAD.
and then argue over whether these are or should be publishable, etc.
In summary --- AARRGH! A correlation, in itself, is neither good/bad nor publishable/unpublishable. One needs to know the "significance level" and/or such extra information such as the design/size of the experiment/survey yielding the correlation. One also needs to know what is being claimed for the correlation (in terms of explanatory or descriptive power) as to get some insight into the reaction of a reviewer/editor.
You're spoiling all the fun! I wanted to see if he had learnt enough in his stats classes to ask about the significance of the results. Seriously, though, the statistical significance of Pearson's r is somewhat problematical. We can work out the probability of getting a value as large in magnitude if we had two independent normal distributions. For the two cited correlations this probability is about 0.1 (i.e borderline significance). But it seems unlikely that gun ownership across nations is a normally distributed random variable. After all, if I don't exclude outliers, the correlation between handgun ownership and homicide is 0.73 with p=0.003.
I think it better to use Spearman's rank correlation coefficient to test for significance.
For handguns vs homicide I get 0.38, p=0.18 (ie not significant)
For all guns vs homicide I get 0.7, p=0.02 (significant)
