A scatter diagram of height against mass for 30 animals contains two distinct clusters. The animals in one cluster are juveniles and those in the other are adults. A single regression line fitted to all 30 points has strong positive correlation.
Explain why fitting one regression line to all 30 animals may be misleading.
Suggest a more appropriate analysis.
Explain why the strong correlation does not establish that increasing an animal's mass causes it to grow taller.