SCIENTIFIC METHOD PRACTICE
For each of the following, indicate whether the statement would be useful as a scientific hypothesis. Remember that a hypothesis must be testable and falsifiable (able to be proved incorrect). If you do not think that a statement is testable or falsifiable, indicate the reason why.
1. Crime rates increase during the full moon.
2. Positive emotions prolong life.
3. The extinct dodo is closely related to other large flightless birds, such as ostriches and rheas.
4. People with larger heads have higher IQs.
Identify the dependent and independent variables in the following experiments:
5. The rate of carbon dioxide produced for yeast cells growing with and without the spice cinnamon.
INDEPENDENT VARIABLE:
DEPENDENT VARIABLE:
6. Number and size of cubs born to polar bears living in habitats reduced by melting sea ice.
INDEPENDENT VARIABLE:
DEPENDENT VARIABLE:
7. The beak length for ground finches recorded over 3 years.
INDEPENDENT VARIABLE:
DEPENDENT VARIABLE:
Suggest a control group that could be used for each of the following experiments. For each of the experiments, explain why you chose the control group you did.
8. Rats are fed artificial sweeteners to determine if the sweeteners cause cancer.
9. Alzheimer patients aged 40-55 are tested for the presence of three copies of chromosome 21.
10. Black worms are exposed to a solution of saline. Worm heart rates are recorded at 2-minute intervals.
11. Frogs are captured from ponds where the parasitic worm Robeiroia is abundant. The number of limb deformities is recorded.
Identify the parts of each of the following experiments.
EXPERIMENT 1: John wanted to know if there would be a difference in the rate that tomato plants would grow at different temperatures. He thought that if tomato plants were grown at warmer temperatures, then they would grow faster. He took one tomato plant and put it at room temperature (72°F) and put a second tomato plant in a room where the heater was on (85°F). He measured the height of the plants every 3 days for 4 weeks.
QUESTION:
HYPOTHESIS:
INDEPENDENT VARIABLE:
DEPENDENT VARIABLE:
CONSTANTS (3 or more):
CONTROL GROUP:
EXPERIMENTAL GROUP:
POSSIBLE SOURCES OF ERROR:
EXPERIMENT 2: Sara was curious about whether plants needed day AND night to grow. She thought that if she grew plants under light 24 hours a day, then they would grow faster. She took three plants put them outside, where they would get night and day. She took three plants and put them in a room where she left the lights on all the time. She counted how many leaves the plants had every 3 days.
QUESTION:
HYPOTHESIS:
INDEPENDENT VARIABLE:
DEPENDENT VARIABLE:
CONSTANTS (3 or more):
CONTROL GROUP:
EXPERIMENTAL GROUP:
POSSIBLE SOURCES OF ERROR:
EXPERIMENT 3: Mike had heard that eating chocolate would make you smarter. He decided to test the speed that rats could run through a maze before and after eating chocolate. He thought that rats would run through the maze more quickly if they had eaten chocolate. He timed a rat as it ran through a maze, then he fed it chocolate and timed it again as it ran through the same maze.
QUESTION:
HYPOTHESIS:
INDEPENDENT VARIABLE:
DEPENDENT VARIABLE:
CONSTANTS (3 or more):
CONTROL GROUP:
EXPERIMENTAL GROUP:
POSSIBLE SOURCES OF ERROR:
EXPERIMENT 4: The class wanted to know who in the class could jump the highest. We hypothesized that it would be the person with the longest legs. We measured the length of each student’s legs and then measured the height that each student could jump.
QUESTION:
HYPOTHESIS:
INDEPENDENT VARIABLE:
DEPENDENT VARIABLE:
CONSTANTS (3 or more):
CONTROL GROUP:
EXPERIMENTAL GROUP:
POSSIBLE SOURCES OF ERROR: