Types of Variables
A scientist wants to determine if the amount of sleep a student gets will affect his test scores. He has one group of students sleep for 6 hours, and another group sleep for 8 hours. Then, he records the grade that each student got on his math test. What is the dependent variable?
Math test scores
A company wants to test if their new drug is effective at treating hair loss. They find 1000 people experiencing hair loss. 500 people receive the drug, and 500 people receive a placebo. Which group is the experimental group?
The group that receives the new drug
A doctor wants to know if a new medication will help his patients who experience high blood pressure. What could be his hypothesis?
If my patients use this new medication, then their blood pressure will decrease.
This group does NOT receive the treatment.
Control group
A student wants to determine if exercising before a test improves test scores. He has one friend exercise for 10 minutes before their upcoming math test, and another friend not exercise before the test. He then compares each friends' score. How could this student make their experiment more valid?
More students in each group
A scientist wants to determine what brand of paper towels holds liquid the best. She spills an equal amount of water on each of three identical tables. She uses a different brand of paper towel to wipe up each spill and measures how much liquid is left on each table. What is the independent variable?
Brand of paper towel
10 students do an experiment to determine if listening to classical music while studying improves their test grades. They randomly select 5 students to listen to classical music while studying, and 5 students to study without listening to any music. Afterwards, they record the test grades each student receives. Which is the control group?
The group that does not listen to music
A student wants to know if studying with flashcards is an effective way to prepare for a science test. What could his hypothesis be?
If I study using flashcards, then my science test scores will increase.
This variable is your "data" that you are measuring.
Dependent Variable
Mrs. Smith's science class does an experiment and finds that SuperGrow fertilizer improves plant growth. What could Mr. Greene's science class do to make sure these results are reliable?
Repeat the experiment
Joe's science class does an experiment to determine if the amount of sunlight plants receive affects their height. They grow one plant near the window, and grow an identical plant in a dark corner. After 30 days, Joe measures the height of each plant. What is the dependent variable?
Height of the plants
A researcher wants to determine if meditation improves people's stress levels. He randomly selects 100 people to meditate for 20 minutes each morning. 100 people meditate for just 10 minutes in the morning. A third group of 100 people does not meditate at all. What is the control group?
The group that does not meditate
A pet-owner wants to know if feeding her dog a new brand of dog food will help her dog to lose weight. What could her hypothesis be?
If I feed my dog this new brand of food, then he will lose weight.
This is an educated guess that you are planning to test. It is written as an If ... Then statement.
Hypothesis
William wants to know if the amount of water given to flowers affects their height. He grows 5 sunflowers in his backyard and gives them 10 mg of water each day. He also grows 5 tulips in his school's courtyard and gives them 30 mg of water each day. What is one problem with William's experiment?
He doesn't keep all of the other conditions the same (i.e., type of plants, location that they are grown in, possibly type of soil or amount of sunlight, etc.)
An athlete wants to determine if he runs faster after drinking Gatorade. On one day, he drinks one liter of Gatorade and then records the time it takes him to run one mile. Another day, he drinks one liter of water and then records the time it takes him to run a mile. What is the independent variable?
Type of drink
A scientist wants to determine if applying 10 mg of a new fertilizer will impact plant growth. He grows 10 plants in identical conditions. 5 of these plants receives 10 mg of fertilizer, while another 5 plants do not receive any fertilizer at all. In one week, he measures the height of each plant. What is the experimental group?
The 5 plants that receive the new fertilizer
A teacher wanted to determine if including games in his class improved his students' learning. What could his hypothesis be?
If I include games in my class, then my students will learn more.
This is a term for a harmless pill that does not have any physiologic effects.
Placebo
A company wants to determine if their new vitamins help people to lose weight. They give 50 people their new vitamins, and measure how much weight each of these people lose within 3 months. What is wrong with their experiment?
There is no control group (group who does not take the vitamins) to compare the results to.
Walmart wants to determine if people spend more money if the walls of their store are painted white or light blue. They randomly assign 40 stores into one of two groups. They paint the walls of 20 stores white, and the walls of another 20 stores light blue. A Walmart executive then tracks how much people spent at each store over the course of a month. What is the dependent variable?
Amount people spent / profit
A teacher wants to determine if group projects help her students learn. She has two sections of the same course with similar students in each. She assigns one of her classes a group project, while the students in her other class are assigned to do the same project by themselves. What is the control group?
The class / students who do the project by themselves
A swimmer wanted to determine if eating more protein would improve his freestyle time. What could his hypothesis be?
If I eat more protein, then my freestyle time will improve.
This is the variable that the scientist directly controls in his experiment.
Independent Variable
Billy needs to design a hypothesis for his science class. He says his hypothesis is, "Does being left-handed cause students to have better grades?" What is wrong with Billy's hypothesis?
He wrote it as a question, not an If ... Then statement. His hypothesis could be, "If students are left-handed, then they will receive higher grades."