Answer:
Pulse rates are directly related to caffeine intake.
Step-by-step explanation:
Pulse rates are directly related to caffeine intake.
'Two variables are directly related' imply that : One variable increase, other variable increase & one variable decrease, other variable decrease
'Two variables are inversely related' imply that : One variable increase, other variable decrease & one variable decrease, other variable increase.
As, the experiment observed that, group having caffeine intake had significantly higher pulse rates. So, caffeine intake & pulse rate are directly related.