Question

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

Answer 1

The independent variable is the one that does not change depending on other variables - so here it would be the presence or the absence of caffeine - this is dependent on Tina's actions, but not on other variables in the experiment. The dependent variable is the heart rate - it is assumed to depend on the presence or absence of caffeine. A hypothesis could be that "Caffeine causes an increase of heart rate in earthworms" - and this hypothesis is what the experiment is testing.