In the same science fair, tina ask the question "does caffeine increase the heart rate of an earthworm? " in test 1,she measures the heart rate by looking at the earthworm under a microscopes, the heart rate if 50 beats per minute. in test 2,she places a few drops of caffeine on the earthworms skin and measures the rate again. in this test the heart rate is 68beats per minute
what is the independent variable in this experiment
what is the dependent variable in this experiment
tina's experiment should have included a hypothisis .in a complete sentence, suggest a hypothesis for tina's experiment