Question

Experiment #1

Question: Does penicillin prevent infection?

Hypothesis: If the medicine prevents infection, than the medicine will prevent the growth of bacteria that cause infection.

Experiment: Leo placed two circles of paper in a 500 Petri dish (something used for growing bacteria).In 250 dishes, the paper was soaked with Peniccilin solution and then inoculated with bacteria. The other 250 dishes were soaked in water only and inoculated with same bacteria .All other conditions including light and temperature remained the same. After 48 hours, Leo observed all dishes and noticed there was no bacteria growth in the penicillin dishes a circle. All dishes with water only had large colonies of bacteria growing in them.

　

At the end of the experiment, a circle with a radius of 2cm formed around the circle of paper soaked in penicillin. There were no bacteria growing in the 2cm circle. No change had occurred around the other circle of paper. The bacteria were growing well.

A. What was the independent variable? ______________________________________________________

B. What was the dependent variable? ________________________________________________________

C. What was the control? _____________

　

D. What was the constant

　

E. What type of study is this? Explain