Unit 1

Scientific Method

Steps to the Scientific MethodAsk a QuestionForm a hypothesis (often an if-then statement)

Example: If a plant receives more sunlight, then the plant will grow faster.

Test the hypothesis – experiment, collect dataControl Group vs. Experimental GroupIndependent Variable – things you manipulateDependent Variable – variables that change as a result of

changes in the independent variable (what you measure)Controlled Variable – variables that are kept the same so

that they do not affect how the independent variable is changed

Draw Conclusions

Independent Vs. Dependent Variables

A developmental psychologist is examining problem-solving ability for grade school children. Random samples of 5-year-old, 6-year-old, and 7-year-old children are obtained. Each child is given a standardized problem-solving task, and the psychologist records the number of errors. Independent Variable? Dependent Variable?

A scientists wants to determine how salt water effects plant growth. He waters plants with different concentrations of salt water and collects data on plant growth. Independent Variable? Dependent Variable? What variables would you keep constant? What is the control group?

GRAPHING DATA

EXAMPLE DATA

SALT WATER CONCENTRATION

(%)

PLANT GROWTH (CM)

0 % 20 cm2 % 16 cm5 % 8 cm8 % 3 cm

12 % 0 cm

ScenariosAaron loves to garden and wants to grow lots of

pink flowers for his pal Sandy. He bought a special Flower Power fertilizer to see if it will help plants produce more flowers. He plants two plants of the same size in separate containers with the same amount of potting soil. He places one plant in a sunny window and waters it every day with fertilized water. He places the other plant on a shelf in a closet and waters it with plain water every other day.

What did Aaron do wrong in this experiment? Explain.

ScenariosPatrick loves bubble gum and would like to be able to blow bigger bubbles than anyone else in his class. To prepare for the school’s Big Bubble Contest, he bought five different brands of bubble gum and needs your help to find the brand that creates the biggest bubbles. Write an experiment to test the bubble power of the bubble gum brands and help Patrick win the contest.

Experimental Design

Marie and Bob buy identical red T-shirts. A month later, Marie and Bob both happen to wear their T-shirts on the same day. Marie notices that Bob’s shirt is a lighter shade of red.

1. Come up with a testable hypothesis (If-then statement)

2. What is the Independent variable?

3. What is the Dependent variable?

4. What are the Controls?