I work with obesity in cats and many studies use a body condition score (BCS) to assess obesity. This is a somewhat subjective measure of how much fat covering an animal has. There are two commonly used scoring systems for BCS (out of 5 and out of 9).
Does the number of categories have an impact on Spearman correlation between the ordinal ranking out of 5 or 9 and the body fat percent?
EDIT: I am mostly wondering what I should get from the results I am reading. One study will list a Spearman-rank correlation between BCS out of 9 and % body fat of 0.84 with a correlation of 0.72 between weight and % body fat. Another study will list the correlation between BCS out of 5 and % body fat of 0.78 and a correlation of 0.74 between weight and % body fat. Would these differences in correlation with %body fat be expected from the number of categories chosen?