What is the scientific method? The scientific method is a process for experimentation that is used to explore observations and answer questions.
Practice Problems
1. Mary investigated the effect of different concentrations of Miracle Grow on the growth of tomato plants. Mary hypothesized that if higher concentrations of Miracle Grow were added, the plants would exhibit poorer growth. She grew four groups of tomato plants (10 plants/group) for 30 days she then applied Miracle Grow as follows: Group A, 0% Miracle Grow; Group B, 10% Miracle Grow; Group C, 20% Miracle Grow; and Group D, 30% Miracle Grow. The plants received the same amount of sunlight and water each day. at the end of 30 days, Mary recorded the height of the plants (in centimeters) and the color of the leaves (green, yellow-green, yellow, or brown). a. In this scenario, what is the independent variable?
b. What is the dependent variable?
c. In this scenario, what are the controlled variables? (identify at least three).
d. Which group would be the control group in this experiment?
2. Different rose bushes are grown in a greenhouse for two months. The number of flowers on each bush is counted at the end of the experiment. a. Independent Variable: b. Dependent Variable: c. Control Variable:
3. You water three sunflower plants with salt water. Each plant receives a different concentration of salt solutions. A fourth plant receives pure water. After a two-week period, the height is measured. a. Independent Variable: b. Dependent Variable: c. Control Variable:
4. Three redwood trees are kept at different humidity levels inside a greenhouse for 12 weeks. One tree is left outside in normal conditions. Height of the tree is measured once a week. a. Independent Variable: b. Dependent Variable: c. Control Group:
5. Pea plant clones are giving different amounts of water for a three-week period. The first pea plant receives 400 milliliters a day. The second pea plant receives 200 milliliters a day. The third pea plant receives 100 milliliters a day. The fourth pea plant does not receive any extra water; the plant only receives natural ways of receiving water. The height of pea plants is recorded daily. a. Independent Variable: b. Dependent Variable: c. Control Group:
6. One tank of gold fish is fed the normal amount of food one a day, a second tank is fed twice a day, and a third tank four times a day during a six week study. The fish's weight is recorded daily. a. Independent Variable: b. Dependent Variable: c. Control Variable:
7. You decide to clean the bathroom. You notice that the shower is covered in a strange green slime. You decide to try to get rid of this slime by adding lemonade juice. You spray half of the shower with lemonade juice and spray the other half of the shower with water. After 3 days of spraying equal amount 3 times a day, there is no change in the appearance of the green slime on either side of the shower. a. Independent Variable: b. Dependent Variable: c. Control Group:
8. You want to test which size of soccer (football) ball is easiest to juggle with your feet. You test size 3, size 4, and a size 5 ball. You count the seconds that ball stays in the air for each of the trials. You allow yourself to use both of your feet, knees, and head to juggle the ball. a. Independent Variable: b. Dependent Variable: c. Control Variable: