NAME: ______PD: _____ DATE: ______

EXPERIMENTAL DESIGN WORKSHEET: IV, DV, CONTROLS, AND CONTROL GROUPS

DIRECTIONS: Use each description and/or data table to help you identify or describe each of the following. Make sure your answers are specific. (not all experiments have a control group)

1.  FISH EGGS: A scientist knows that the percent of fish eggs that hatch is affected by the temperature of the water in an aquarium. She is attempting to identify which water temperature will cause the highest percentage of fish eggs to hatch. The scientist sets up 5 aquariums at the following temperatures: 10°C, 20°C, 30°C, 40°C, and 50°C. She adds 50 fish eggs to each aquarium and records the number of eggs that hatch in each aquarium.

A.  Independent variable(s): ______

B.  Dependent variable: ______

C.  List 3 variables that should be controlled (held constant): ______

D.  Describe any control group(s) in the experiment (if one doesn’t exist, leave this section blank):

______

2.  GAS MILEAGE: A car magazine is trying to write an article that rates the top 5 most fuel efficient SUVs (the SUVs that can drive the most miles for each gallon of gasoline). They make sure each model of SUV has exactly 10 gallons of gasoline in its fuel tank and reset the odometer (instrument that measures the distance a vehicle has traveled) to zero. The SUVs are then driven until they run out of gasoline. The distance on the odometer is recorded.

A.  Independent variable(s):______

B.  Dependent variable: ______

C.  List 3 variables that should be controlled (held constant): ______

______

D. Describe any control group(s) in the experiment blank:

______

mouthwash
used / time mouthwash
was in mouth / # of bacteria in
mouth (average)
none / 60 sec. / 135
A / 60 sec. / 23
B / 60 sec. / 170
C / 60 sec. / 84
D / 60 sec. / 39
E / 60 sec. / 81

3.  MOUTHWASH: The makers of brand A mouthwash want to prove that their mouthwash kills more bacteria than the other 4 leading brands of mouthwash. They organize 60 test subjects into 6 groups of 10 test subjects. The data for the experiment is shown to the right.

A.  Independent variable(s): ______

B.  Dependent variable: ______

C.  List 3 variables that should be controlled (held constant): ______

D.  Describe any control group(s) in the experiment blank:

______

PART II- DRAWING CONCLUSIONS---Quite a few Heritage High School teachers/staff have been busy doing a little research. Read the description for each experiment and answer the questions.

4.  Did you just fart?----Mr. Oshodi wants to reduce the number of students with flatulence at HHS. He has created a new sauce that he thinks will reduce the production of body gas associated with eating the delicious lunch items offered on campus. He recruits 100 students with a history of gas problems. He has 50 of them (Group A) eat pizza with the new sauce. The other 50 (Group B) eat pizza with sauce that looks just like new sauce but is really just mixture of mayonnaise and food coloring. Both groups were told that they were getting the sauce that would reduce gas production. Two hours after eating the pizza, 30 students in group A reported having fewer gas problems and 8 students in group B reported having fewer gas problems.

A.  Which people are in the control group? ______

B.  What is the independent variable? ______

C.  What is the dependent variable? ______

D.  What should Mr. Oshodi’s conclusion be? ______

E.  Why do you think 8 students in group B reported feeling better?______

5.  Halitosis. Your breath; it smells! ---Mr. Holmes notices that his pal Mr. #$%@ (shall remain anonymous) is suffering from severe halitosis, which occurs when one doesn’t brush his or her teeth regularly. Mr. Holmes is tired of smelling his friend’s nasty breath so he decides to see if he can help cure his friend’s bad breath by making his friend brush his teeth every day. Mr. Holmes decides to test his hypothesis by brushing Mr. #$%@ (shall remain anonymous) teeth with toothpaste for 2 weeks straight. After a 2 weeks of treatment, the horrible smell is gone and Mr. #$%@ (shall remain anonymous) breath smells minty fresh.

A.  What was the initial observation? ______

B.  What is the independent variable? ______

C.  What is the dependent variable? ______

D.  What should be Mr. Holmes’ conclusion ______

6.  Does this make my muscles look big?

Ms. Davies was told that a certain muscle cream was the newest and best thing on the market. It claims to double a person’s muscle power when used as part of a muscle-building workout. Interested in this product, she buys the special muscle cream and recruits Mr. Beyer and Mr. Schneider to help him with an experiment. Ms. Davies develops a special weight-lifting program for Mr. B and Mr. S. She meets with them once every day for a period of 2 weeks and keeps track of the number of 100lb triceps curls done in 1 minute. Before each session Mr. Beyer’s arms and back are lathered in the muscle cream, while Mr. Schneider’s arms and back are lathered with the regular lotion.

A.  Which person is in the control group? ______

Time / Mr. Beyer / Mr. Schneider
Initial Amount / 18 / 5
After 1 Week / 24 / 9
After 2 Weeks / 33 / 17

B.  What is the independent variable? ______

C.  What is the dependent variable? ______

D.  What should Ms. Davies’ conclusion be? ______

7.  Microwave Miracle?

Mrs. Hinojosa believes that fish that eat food exposed to microwaves will become smarter and would be able to swim through a maze faster. She decides to perform an experiment by placing fish food in a microwave for 20 seconds. She has the fish swim through a maze and records the time it takes for each one to make it to the end. She feeds the special food to 10 fish and gives regular food to the 10 others. After 1 week, she has the fish swim through the maze again and records the times for each.

A.  What was Mrs. Hinojosa’s hypothesis? ______

______

B.  Which fish are in the control group? ______

C.  What is the independent variable? ______

D.  What is the dependent variable? ______

E.  Look at the results in the charts. What should Mrs. Hinojosa’s conclusion be? ______

______

8.  Aloe Cures All!--- Mrs. Pennington read that aloe vera promoted healing of burned tissue. She decided to investigate the effect of varying amounts of Aloe Vera on the regeneration of the flat worm, planaria. She bisected the planaria to get 10 parts (5 heads and 5 tails) for each experimental group. She applied 15ml of aloe vera concentrations of 0%, 10%, 20%, and 30% Aloe Vera to the groups. All planarians were maintained in a growth chamber with identical food, temperature, and humidity. On day 15, Mrs. Pennington observed the regeneration of the planaria parts and categorized development as full, partial or none.

A.  Title: ______

B.  Hypothesis: ______

C.  Independent variable(s): ______

D.  Dependent variable: ______

E.  List 3 variables that should be controlled (held constant): ______

F.  Describe any control group(s) in the experiment blank): ______

Answer Key

1 – Did you fart?

Which people are in the control group? Group B

What is the independent variable? New sauce

What is the dependent variable? Amount of gas

What should Mr. Krabs’ conclusion be? The new sauce appears to work as it reduced the amount of gas produced in 60% of the people tested.

Why do you think 10 people in group B reported feeling better? They thought they were getting the new sauce as a result thought that they didn’t have as much gas. (Placebo effect)

2 – Halitosis

What was the initial observation? Slimotosis on Gary’s shell

What is the independent variable? Cures (Seaweed and Dr. Kelp)

What is the dependent variable? Slime and odor

What should Sponge Bob’s conclusion be? Although Gary’s symptoms have disappeared, it is not known which cure was the one that worked. He should redo the experiment and include a control group as well as two other testing groups for each of the proposed cures.

3 – Muscles

Which person is in the control group? Mr. Schnieder

What is the independent variable? Muscle cream

What is the dependent variable? Amount of reps lifted (strength)

What should Larry’s conclusion be? Since both Patrick and SpongeBob improved their results by the end of two weeks, it does not appear that the claims for the special muscle cream are true. If the claims were correct, we should have seen Patrick’s amount double, but not SpongeBob’s amount. The improvements were likely a result of Larry’s special workout.

4 – Microwave Miracle

What was Patrick’s hypothesis? He hypothesized that feeding fish microwaved food would make them become smarter.

Which fish are in the control group? The fish that eat regular food

What is the independent variable? Microwaved food

What is the dependent variable? Time required to complete the maze

Look at the results in the charts. What should Patrick’s conclusion be? According to the data, all but two fish in each group decreased their time through the maze. The special food does not appear to be a big factor in helping fish become smarter.

Note: Of the fish that did improve their times, the fish that were fed the special food averaged a 9.625 seconds decrease in their times compared to an average decrease of 6.625 seconds in the fish group that received the regular food. This does show a slight improvement for the microwaved food group, but not enough to prove that his hypothesis was correct. More testing would need to be done