Hypothesis a: if heart rate is related to caffeine intake, then coffee drinkers will have higher heart rates.
hypothesis b: if a higher heart rate is related to caffeine intake, then the heart rate of most people will be higher 30 minutes after they drink a cup of coffee.

which hypothesis is more useful and why?

a. the two hypotheses are equally useful.
b. hypothesis a is more useful because it’s true.
c. neither hypothesis is useful because they aren’t testable.
d. hypothesis b is more useful because it suggests a way to test the relationship between heart rate and caffeine intake.