Experimental Design.... HELP PLEASE WITH THE LAST TWO PLEASE!!!!!

Question

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                                                                    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

Answer 1

Fish Experiment:

 

The independent variable is the temperature.

 

The dependent variable is the number of eggs that hatch.

 

Some controlled variables could be lighting, pH, and oxygen concentration in the water.

 

There are no controls for this experiment.

 

 

Mileage Experiment:

 

The independent variable is the model of SUV.

 

The dependent variable is the distance each SUV gets.

 

Some controlled variables would be road conditions, weather conditions, and type of terrain (country vs. city, hilly vs. flat).

 

There is no control group for this experiment.

 

 

Mouthwash Experiment:

 

The independent variable is the mouthwash brand used. 

 

The dependent variable is the amount of bacteria killed.

 

Some controlled variables would be the health of the subjects, the time of day of the experiment (morning vs. night), and the condition of the mouth before treatment (after eating, after brushing, etc.).

 

The control group is the one that doesn't use the mouthwash.