TOPIC: Scientific Method AIM: What are the steps of the Scientific Method?

Model, or guide used to solve problems and to get information What is the Scientific Method? Model, or guide used to solve problems and to get information

Always in the form of a question What you want to solve STEPS Problem Always in the form of a question What you want to solve

Under what color light will plants grow best? Problem Under what color light will plants grow best?

Suggested answer to the problem HOW? Research problem 2. Hypothesis EDUCATED GUESS Suggested answer to the problem HOW? Research problem

Hypothesis I think the plant under green light will grow best because plants are green.

TEST IF HYPOTHESIS IS RIGHT OR WRONG 3. Experiment TEST IF HYPOTHESIS IS RIGHT OR WRONG Gather materials Design procedures Record results

Experiment Grow the plants for 5 weeks. Each is placed under a certain color light. They will get the same amount of light, & will be watered every 2 days. Their height will be measured (in centimeters) once a week.

Organize and analyze data How? Graphs, charts… 4. Observation

Observations 1 2 3 4 5 6 PLANTS Height (cm) Growth of plants 12 10 8 6

Is hypothesis right or wrong? 5. Conclusion Explains data Is hypothesis right or wrong? Answers the question stated in the problem

Conclusion My hypothesis was wrong. Plants grow best under blue light, not green light. The plant under blue light grew 11cm while the plant under green light grew only 2 cm.

A hypothesis supported by many experiments What is a THEORY? A hypothesis supported by many experiments Thought to be true but can be changed

A statement that is believed to be true What is a LAW? A statement that is believed to be true

People Hate Elephants On Couches PROBLEM HYPOTHESIS EXPERIMENT OBSERVATION CONCLUSION

2 groups: 1. Experimental group = contains the VARIABLE Controlled

2. Control group = does not contain the variable used to compare (normal setup)

Factor that changes in each set up Variable Factor that changes in each set up

Everything between the 2 groups must be exactly the same except for the variable!!!

2 types of variables: 1. Independent Variable = the 1 factor that’s different between experimental group and control group

Independent variable = ? SUNLIGHT

data or results obtained 2. Dependent Variable = what is measured data or results obtained HEIGHT

EX #1: Does beta-carotene protect against cancer? Beta-carotene supplements have been thought to protect against cancer. But one study suggests this is false. The study was conducted with 39,000 women aged 45 and up. These women were randomly assigned to receive a beta-carotene supplement or a placebo. Their health was studied over their lifetime. Cancer rates for women taking the beta-carotene supplement did not really differ from the cancer rates of those women taking the placebo. What is the independent variable? supplements: beta-carotene What is the dependent variable? How many patients got cancer

Use a larger sample size Use only one variable What must be done to make results of an experiment more reliable or valid? Repeat experiment Use a larger sample size Use only one variable

What is the independent variable? Substance Z Ex # 2: To investigate the effect of a substance on plant growth, 2 bean plants of the same species were grown under identical conditions with Substance Z added to the soil of one of the plants. At the end of 2 weeks, the plant grown with Substance Z was 12.5 cm tall. The plant grown without Substance Z was 12.2cm tall. The researcher concluded that the presence of Substance Z causes the plants to grow taller. What is the independent variable? Substance Z What is the dependent variable? height Which setup is the control? Plant without Substance Z

Example #3 How bright is right? An automobile manufacturer wants to know how bright brake lights should be in order to minimize the time required for the driver of a following car to realize that the car in front is stopping and to hit the brakes. What is the independent variable? brightness of brake light What is the dependent variable? time to hit brake

Ex #4: A student placed 5 geranium plants of equal size in 5 environmental chambers. Growing conditions were the same for each plant except for the amount of water each received. At the end of 20 days, plant growth was measured. What is the independent variable? Amount of Water What is the dependent variable? growth

5. An investigation was designed to determine the effect of ultraviolet light on mold spore growth. Two groups of mold spores were grown under identical conditions, except one group was exposed only to ultraviolet light, while the other group was grown in total darkness. In this investigation, the group of mold spores grown without receiving any ultraviolet light is known as the a. experimental variable b. hypothesis c. control d. limiting factor

6. Which sentence represents a hypothesis? a. Environmental conditions affect germination. b. Boil 100 milliliters of water, let it cool, and then add 10 seeds to the water. c. Is water depth in a lake related to available light in the water? d. A lamp, two beakers, and elodea plants are selected for the investigation.