Name: Period: Date: Score: Writing an If Then Hypothesis Purpose: To learn how to write testable hypotheses. When using the scientific method to conduct an experiment, you do not always know the results of the lab; however, you can independently find a verifiable answer. In real experiments, real hypotheses should be written before the actual experiment. What Is a Real Hypothesis? A hypothesis is a statement that proposes a possible explanation to some phenomenon or event. A useful hypothesis is a testable statement which may include a prediction. It predicts the relation between two variables. Write answers next to each question. Answers were discussed in class. 1) What is a variable in Science? 2) What are the three types of variables? A hypothesis statement must be testable. That is, you will perform a test of how two variables (independent and dependent) might be related. This is when you are doing a real experiment. You are testing variables. Usually, a hypothesis is based on some previous observation such as noticing that in November many trees undergo color changes in their leaves and the average daily temperatures are dropping. Are these two events connected? How? Any laboratory procedure you follow without a hypothesis is really not an experiment. It is just an exercise or demonstration of what is already known. How Are Hypotheses Written? All of the examples on the next page are examples of hypotheses because they use the word "may." However, their form is not particularly useful. Using the word may does not suggest how you would go about proving or testing it. Good hypotheses contain two variables. One is "independent" and the other is "dependent." The independent variable is the one you, the "scientist" control and the dependent variable is the one that you observe and/or measure the results. Use quantitative indicators such as increasing/decreasing before the independent variable and state how the dependent behavior will respond. In the hypothesis about skin cancer below, the independent variable is single underlined and the dependent variable is double underlined.
Example of a Testable Hypothesis: If skin cancer is related to ultraviolet light, then people with a high exposure to uv light will have a higher frequency of skin cancer. Notice that these statements contain the words if and then. They are necessary in a good hypothesis. But not all if-then statements are hypotheses. For example, "If I play the lottery, then I will get rich." The previous statement - If I play the lottery, then I will get rich - is a simple prediction and not a hypothesis. Why? Let s Practice: A) In the table below, rewrite the 6 hypotheses using the if then style shown. B) Single underline the independent variable and double underline the dependent variable in the hypothesis YOU WRITE in the table. 1. 2. 3. 4. 5. 6. 1. Chocolate may cause pimples. 2. Acid in soil may affect plant growth. 3. Watching TV leads to bad grades. 4. Bacterial growth may be affected by temperature. 5. Ultra violet light may cause skin cancer. 6. Temperature may cause leaves to change color. B) Write a hypothesis statement for each of these questions - Going from a question to a hypothesis: 1) Does temperature affect the performance of a track athlete in a 100 m race? 2) Does cell phone usage cause car accidents? 3) Does spending more time on Homework increase your chances of getting an A in Biology?
C) Now, for each of these hypotheses, think about what your controlled variables need to be in the experiment? List 2 controlled variables for TWO of your hypotheses. Rewrite one hypothesis here: Controlled Variable 1: Controlled Variable 2: Rewrite one hypothesis here: Controlled Variable 1: Controlled Variable 2:
Identifying Scientific Variables Read through each of the experiments conducted by Bart Simpson and his TV gang and answer the questions in the space provided. You do not need to use complete sentences. Smithers made a new special drink called WORKEZ. He thinks that this special juice will increase the speed of his office workers. He creates two groups (A and B) 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. Result: Group A made 1,587 stacks, Group B made 2,113 stacks. Identify the: 1. Control Group - 2. Independent Variable 3. Dependent Variable 4. Write Smithers hypothesis (use If then ): 5. What should Smithers conclusion be? 6. How could this experiment be improved? 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. Result: After 3 days of treatment there is no change in the appearance of the green slime on either side of the shower. 7. What was the initial observation? Identify the- 8. Control Group 9. Independent Variable 10. Dependent Variable 11. Write Homer s hypothesis: 12. What should Homer s conclusion be?
Bart believes that mice exposed to microwaves will become extra strong (maybe he s been reading too much Radioactive Man!). He decides to perform this experiment by placing 10 mice in a microwave for 10 seconds (don t try this at home!). He compared these 10 mice to another 10 mice that were not put in the microwave. He tested the strength of the 2 groups of mice by placing a wood piece blocking its food. Result: Bart found that 8 out of 10 of the microwaved mice were able to push the block away. 7 out of 10 of the non-microwaved mice were also able to push the wood block away. Identify the 13. Control Group 14. Independent Variable 15. Dependent Variable 16. Write Bart s hypothesis ( If then. ): 17. What should Bart s conclusion be? 18. How could Bart s experiment be improved? Krusty saw an advertisement that a certain itching powder SCRATCHOMATIC was the newest best thing on the market, it even claims to cause 50% longer lasting itches. Interested in this product, he buys SCRATCHOMATIC and compares it to another product ITCHKING. One test subject (A) is sprinkled with ITCHKING itching powder, and another test subject (B) was sprinkled with SCRATCHOMATIC itching powder. Result: Subject A reported having itches for 30 minutes. Subject B reported to have itches for minutes. Lisa is working on a science project. Her task is to answer the question: Does Rogooti (which is a commercial hair product) affect the speed of hair growth? Her family is willing to volunteer for the experiment. Identify the - 19. Control Group 20. Independent Variable 21. Dependent Variable 22. Write Krusty s hypothesis ( If then. ): 23. Explain whether the data supports the advertisement s claims about its product SCRATCHOMATIC. 24. Identify the control group, and the independent and dependent variables in your description. Write the hypothesis. Describe how the experiment will be performed. (Can write below use binder paper if necessary).