Question

scenario
a company wants to test a new dog food that is supposed to help overweight dogs lose weight. 50 dogs are chosen to get the new food, and 50 more continue their normal diets. after one month, the dogs are checked to see if they lost any weight.
a new sunscreen has been developed that is supposed to be more effective at preventing sunburn. 30 participants spray one arm with the new formula, and spray the other arm with the leading formula. after 4 hours in the sun, their skin is evaluated for any redness.
a student wants to study the effect of sunlight on plant growth. in his experiment, 12 plants receive normal amounts of sunlight, but half of them are kept under bright sun lamps all night long. after 6 weeks, the plants’ heights are measured.

independent variable
14.
18.
22.

dependent variable
15.
19.
23.

experimental group
16.
20.
24.

control group
17.
21.
25.

©2015 adventures in science

Explanation:

Scenario 1 (Dog Food):

• Independent Variable (14): The type of dog food (new food vs. normal diet). It's the factor manipulated.
• Dependent Variable (15): The dogs' weight loss. It's what's measured based on the independent variable.
• Experimental Group (16): Dogs given the new food (50 dogs). They receive the treatment.
• Control Group (17): Dogs given normal diets (50 dogs). They don't get the new food, for comparison.

Scenario 2 (Sunscreen):

• Independent Variable (18): Sunscreen formula (new vs. leading). It's the manipulated factor.
• Dependent Variable (19): Skin redness (sunburn). It's the measured outcome.
• Experimental Group (20): Arms sprayed with new sunscreen. They receive the new treatment.
• Control Group (21): Arms sprayed with leading sunscreen. They use the existing product for comparison.

Scenario 3 (Plant Sunlight):

• Independent Variable (22): Sunlight duration (normal vs. all night). It's the manipulated factor.
• Dependent Variable (23): Plant height. It's the measured outcome.
• Experimental Group (24): Plants under sun lamps all night. They receive the altered sunlight.
• Control Group (25): Plants with normal sunlight. They have the standard condition for comparison.

Answer:

Scenario 1 (Dog Food)

1. Independent Variable: Type of dog food (new food vs. normal diet)
2. Dependent Variable: Dogs’ weight loss
3. Experimental Group: Dogs given new food
4. Control Group: Dogs given normal diets

Scenario 2 (Sunscreen)

1. Independent Variable: Sunscreen formula (new vs. leading)
2. Dependent Variable: Skin redness (sunburn)
3. Experimental Group: Arms with new sunscreen
4. Control Group: Arms with leading sunscreen

Scenario 3 (Plant Sunlight)

1. Independent Variable: Sunlight duration (normal vs. all night)
2. Dependent Variable: Plant height
3. Experimental Group: Plants under sun lamps all night
4. Control Group: Plants with normal sunlight