Among the two strongest correlations reported, which had the higher correlation coefficient?

• A. % primary BAs in feces vs fecal DI (ρ = 0.65)
• B. log C. hiranonis vs % secondary BAs (ρ = 0.75)
• C. ASBT protein vs ASBT mRNA (ρ = 0.41)
• D. CIBDAI vs ASBT protein (not specified)

Answer: (B)

Correlation strength is determined by how close the correlation coefficient is to 1 in magnitude. Here, the two strongest relationships have coefficients of 0.75 and 0.65, with the higher one being 0.75. This is the link between log abundance of Clostridium hiranonis and the percentage of secondary bile acids. A coefficient of 0.75 indicates a tight, consistent positive relationship: as the abundance of C. hiranonis increases (on a log scale), the proportion of secondary bile acids rises in a predictable way. This makes sense biologically because C. hiranonis is involved in converting primary bile acids to secondary bile acids, so their abundances track together tightly.

In contrast, the relationship between percent primary bile acids in feces and fecal DI, while still strong at about 0.65, is not as tight as the 0.75 pairing. The weaker correlation between ASBT protein and ASBT mRNA (around 0.41) reflects the fact that mRNA levels do not perfectly predict protein expression, likely due to post-transcriptional regulation or other factors affecting protein abundance.