Tail-feather length in birds is sometimes a sexually dimorphic trait. That is, the trait differs substantially for males and for females. Researchers studied the relationship between weight (x) and tail-feather length (y) in a sample of five wild male long-tailed finches. Here are the data:
What are the units of the correlation coefficient for these data?
$$\begin{array} { c c }
\text { weight } ( \mathrm { g } ) & \text { tail length } ( \mathrm { mm } ) \
20.8 & 82.5 \
19.1 & 82.5 \
15.9 & 67.0 \
16.7 & 70.5 \
15.7 & 73.5
\end{array}$$

Question

Tail-feather length in birds is sometimes a sexually dimorphic trait. That is, the trait differs substantially for males and for females. Researchers studied the relationship between weight (x) and tail-feather length (y) in a sample of five wild male long-tailed finches. Here are the data:
What are the units of the correlation coefficient for these data?
 $$\begin{array} { c c } 
\text { weight } ( \mathrm { g } ) & \text { tail length } ( \mathrm { mm } ) \
20.8 & 82.5 \
19.1 & 82.5 \
15.9 & 67.0 \
16.7 & 70.5 \
15.7 & 73.5
\end{array}$$

Quizplus · Accepted Answer

Correlation coefficient is a unitless quantity, meaning it does not depend on the units used to measure the variables being correlated. Therefore, the answer is choice D.

Tail-Feather Length in Birds Is Sometimes a Sexually Dimorphic Trait