Independent and Dependent Variables: Practice Worksheet

Name: Date: Aim: H ow can we identify the relationships between variables on a graph?

STATION 1 - Read the following experiments and answer the related questions.

1. Suzie Q wants to know how different colors of light effect the growth of plants. She believes that plants can survive the best in white light. She buys 5 ferns of the same species, which are all approximately the same age and height. She places one in white light, one in blue light, one in green light, one in red light and one in the closet. All of the ferns are planted in Miracle-Grow and given 20 mL of water once a day for 2 weeks. After the two weeks, Suzie observes the plants and measurements. a. What measurements could Suzy make to determine how different colors of light affect the growth of plants? Suzie should measure the heights of each plant in centimeters at the end of the two weeks.

b. What is the independent variable? Color of light c. What is the dependent variable? Height/Growth of the plants d. What was the control group in this experiment? The plant in the closet (didn’t receive any light) e. List 3 variables that should be held constant in this experiment?

1) Type of Plant (same initial height and age).

2) Type of fertilizer used (Miracle-Grow).

3) Amount of water (20 mL).

2. 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) What is the Independent variable? Brand of Mouthwash

b) What is the Dependent variable? # of bacteria in mouth

c) What was the control group in this experiment? The group that didn’t use mouthwash.

d) List 3 variables that should be held constant in this experiment:

1) Each person should use the same amount of mouthwash.

2) Each person should use the mouthwash for the same amount of time.

3) Each person should use the mouthwash at the same time of day.

3. Smithers thinks that a special juice will increase the productivity of workers. He creates two groups of 50 workers each and assigns each group the same task (in this case, they're supposed to staple a set of papers). Group A is given the special juice to drink while they work. Group B is not given the special juice. After an hour, Smithers counts how many stacks of papers each group has made. Group A made 1,587 stacks, Group B made 2,113 stacks.

Identify the: a. Independent Variable: Smither’s special Juice b. Dependent Variable: Productivity of workers c. Control Group: Group that didn’t drink the juice d. What should Smithers' conclusion be? The special juice did not increase the productivity of the workers; in fact, the group with the juice actually made less stacks of papers than the group that didn’t drink the juice. e. How could this experiment be improved? Smither’s should repeat this experiment but use the same workers both times. He should have 50 workers drink the juice and staple the papers and then have those same 50 workers do the same task without the juice the following day.

4. Homer notices that his shower is covered in a strange green slime. His friend Barney tells him that coconut juice will get rid of the green slime. Homer decides to check this out by spraying half of the shower with coconut juice. He sprays the other half of the shower with water. After 3 days of "treatment" there is no change in the appearance of the green slime on either side of the shower.

Identify the: a. Independent Variable: Use of coconut juice b. Dependent Variable: Amount of green slime c. Control Group: The part of the shower that is sprayed with water. d. What should Homer’s conclusion be? Coconut juice does not get rid of green slime in the shower. 5. Larry was told that a certain muscle cream was the newest best thing on the market and claims to double a person’s muscle power when used as part of a muscle-building workout. Interested in this product, he buys the special muscle cream and recruits Patrick and SpongeBob to help him with an experiment. Larry develops a special marshmallow weight-lifting program for Patrick and SpongeBob. He meets with them once every day for a period of 2 weeks and keeps track of their results. Before each session Patrick’s arms and back are lathered in the muscle cream, while Sponge Bob’s arms and back are lathered with the regular lotion. Identify the: a. Independent Variable: Muscle Cream b. Dependent Variable: Person’s muscle power c. Control Group: Spongebob who used regular lotion. d. What should Larry’s conclusion be? Since both Spngebob and Patrick gained muscle after the 2-week time period, Larry cannot conclude that it is due to the muscle cream. The reason that they both gained muscle is most likely due to the fact that both subjects lifted weights during that time. STATION 2 - Organize the sentence strips into categories based on whether they show a direct, indirect, static or cyclic relationship. Label the relationship shown on each graph in the table & record the examples of each relationship (2 of each type) into your notes once they’ve been checked. GRAPH:

RELATIONSHI DIRECT STATIC INDIRECT CYCLIC P: EXAMPLES: 1. The higher the temperature of the 6. As the mass of a post-it 2. As the time Ms. Kupferman 7. As time in a day air in the oven, the faster a cake will increases, density of the spends at the mall increases, the increases, ocean water bake. post-it remains the same. money in her wallet decreases. levels rise and fall in a predictable pattern. 4. As pressure acting on a soda can 8. As the time Mrs. 3. The more time people spend Hatzichristos spends increases, density of the soda can using social media, the less able 9. As date of the month watching “The Voice” increases.. they are to express themselves in increases, phases of the increases, her singing conversation. ability remains the same. moon repeat in a pattern. 5. As the temperature of air 12. As volume of a piece of quartz increases, its increases, density of the air 11. As the time of year density remains the decreases. changes from September same. 2016 to September 2017, 10. As distance from the equator the temperature in New increases, temperature 13. As the time Mr. York begins to decrease, decreases. Holman spends in the car then increase, and then increases, his distance decrease again. remains the same. Why would this be?  Mr. Holman could have been stuck in traffic. THINK ABOUT IT! Is it possible for data to be represented by the graph to the right? Why or why not? No, it is not possible to have a graph that looks like this because the X-Variable (INDEPENDENT VARIABLE) must always increase. It is the y-variable (DEPENDENT VARIABLE) that changes in response to the x-variable. In this graph, only the y-variable changes, as the x-variable remains the same. STATION 3: Create a graph based on the experiment and data table below.

Problem: Spongebob and Sandy have noticed Patrick has gained weight over the past few months. They believe the cause of his weight gain has to do with his consumption of Krabby Patties at the Krustie Krab. In order to help Patrick lose the weight, Sandy and Spongebob asked Patrick to record his weight and the number of patties he had consumed over a 10- week period. See the results in the data table below. ** Note: When a data point falls between two numbers, you must plot the point between those two numbers on the graph (do not round unless otherwise told to do so). ** 1. What is the independent variable in this experiment? # of Krabby Patties eaten. 2. What is the dependent variable? Patrick’s Weight. 3. Describe the relationship between Krabby Patties consumed and Patrick’s weight. As the number of Krabby patties Patrick eats increases, Patrick’s weight also increases. 4. If Patrick had consumed 15 patties, approximately how much would he weigh? 42 pounds – use the graph to interpolate – see green line above. 5. If Patrick consumed 30 patties, approximately how much would he weigh? In order to extrapolate you would either need more room on the graph or data that has a set trend (each y-variable increases by the same amount), in order to be able to predict Patrick’s weight when 30 patties are consumed. 6. If Patrick measures his weight to be 29 pounds, how many patties did he eat during that week? 6 Krabby Patties – use the graph to interpolate – see yellow line above.

STATION 4: Analyze the following picture and summarize its message. Using the picture as a model, create your own picture using different independent and dependent variables. 1. Summarize the picture: The picture shows a person talking on the phone and then his cell phone bill afterwards.

2. What is the relationship between these two variables? As time spent talking on the phone increases, the cost of your cellphone bill also increases. (DIRECT RELATIONSHIP)

3. Create your own picture on the computer paper provided. Leave your picture in the bin on your desk when finished.

STATION 5: Design an experiment.

• What do you want to test? • Include a hypothesis.

• Identify your independent and dependent variables.

• Make a graph to show the general relationship between the two variables you would be testing.