Question

experiment #1 hypothesis: if penicillin prevents infection, then the growth of bacteria will prevent the growth of bacteria. question: does penicillin prevent infection? experiment: leo placed two circles of paper in a petri dish. one had nothing on it. he placed a drop of bacteria on both circles of paper. the other had penicillin. at the end of the experiment, a circle with a radius of 2cm formed around the circle of paper with penicillin. there were no bacteria growing in the 2cm circle. no change had occurred around the other paper. the bacteria were growing well. a. what was the independent variable? b. what was the dependent variable? c. what was the control? d. was there a constant variable? if yes, explain. experiment #2 hypothesis: do different types of music affect how well a person can do his/her homework? music that does not have a strong beat makes concentrating on a homework assignment easier. music with heavy beats makes concentration more difficult. experiment: sara lilia pulled out four different cd’s to find out which type helped her to finish her homework the fastest. the first cd was rock, the second reggaeton, the third classical, and the fourth was cumbia. she then math assignment that required concentration. each time the alarm went off, sara lilia recorded how many problems she was able to finish. at the end of the experiment, she found that she was able to concentrate the most with the classical music, then the rock, and the cumbia. she noticed that she did not concentrate much at all with the reggaeton and felt like dancing and singing along instead of working. a. what was the independent variable? b. what was the dependent variable? c. what was the control? d. was there a constant variable? if yes, explain. in science experiments, it is very important to “control the variables” so that there is only one independent variable. we “control the variables” by making anything else that could

Explanation:

In an experiment, the independent variable is what is changed or manipulated, the dependent variable is what is measured as a result of the change in the independent variable, the control is a standard for comparison where the independent - variable is not changed, and a constant variable remains the same throughout the experiment. For Experiment #2:

• The independent variable is the type of music as it is being changed to see its effect.
• The dependent variable is how well a person can do their homework (concentration level) as it is being measured.
• There is no clear control in this experiment as there is no situation where no music is played for comparison.
• Constant variables could be the person (Sara Lilia), the amount of time listening to music (5 minutes), and the type of homework (math assignment).

Answer:

Experiment #2:
A. The independent variable: Type of music
B. The dependent variable: Concentration level while doing homework
C. The control: None
D. The constant variable: Sara Lilia, time (5 minutes), type of homework (math assignment)