Scientific Inquiry and Skills

What Is Science? Science seeks to develop explanations using

observations as evidence Evidence: support for the idea that something is

true New information is often combined with

information people already know

Observations and Inferences Observations: things or events that are made

using any of the senses or tools Common tools: thermometers, graduated

cylinders, balance scales, microscopes, and rulers

Better tools lead to better observations Inferences: conclusions or deductions based on

observations

Assumption: the belief that something is trueNot good science

Opinions: ideas that may or not be based on facts

Good experiments avoid opinions

Starting an Experiment Experiment: a series of trials that are done to

support or disprove a hypothesis 1. Form a hypothesis Hypothesis: an educated guess that attempts to

explain what you have observed Begins with “I think that” Never use a question!

2. Set up variables and a control The dependent variable is the observation you

measure Ex: height of a plant The independent variable is the condition that

influences the dependent variableThe variable you change

Ex: the amount of sunlight a plant receives Each experiment can only have ONE

independent variable

The control is portion of the experiment that remains constant

Ex: all plants should be the same kind of plant, receive the same amount of water, and be planted in the same type of soil

The control provides a reference point for comparison

If you add a substance to the experimental group, you need to also add something to the control

When testing medications, the control group is often given a sugar pill called a placebo

Large sample sizes and repeated trials lead to more accurate results

Ex: You will get more accurate results if you test 100 plants in 6 trials than if you tested 2 plants in 1 trial

Sample Experiment #1 Tomato plants are going to be planted in either

the sunny side of the yard or the shaded side of the yard. Design an experiment that will determine the best conditions to grow tomatoes.

Hypothesis: I think that tomatoes grown in the sunny side of the yard will grow more than the tomatoes in the shaded side.

Independent variable: amount of sunlight Dependent variable: the height of the plants Controls: same species of plant, same soil, same

amount of water, same temperature

Sample Experiment #2 A drug company claims that their drug will grow

hair in bald men. 100 men agree to be test subjects. Design an experiment to test the effectiveness of the drug.

Hypothesis: I think that the drug will grow hair in bald men.

Independent variable: 50 men will take the drug; the other 50 will take a placebo

Dependent variable: amount of hair/length of hair that grows

Control: same age, same diet, same health

Collecting and Organizing Data

Data: the results of trials or tests completed during an experiment

Data should be collected into a data table and then transferred to a graph

How to Make a Data Table 1. Pick a title that uses both the independent

and dependent variables. Ex: The Effect of Amount of Sunlight on Plant

Growth 2. Use column headings. Ex: Column 1 = Hours of Sunlight per Day;

Column 2 = Growth of Plant in cm 3. Fill in the data table so that the

independent variable goes in increasing order

Data: 0 hours of sunlight = 0 cm growth; 8 hours of sunlight = 7 cm growth; 10 hours of sunlight = 9 cm growth; 4 hours of sunlight = 3 cm growth; 6 hours of sunlight = 5 cm growth; 12 hours of sunlight = 9 cm growth, 2 hours of sunlight = 1 cm growth.

Hours of Sunlight per Day Plant Growth in cm

The Effect of Amount of Sunlight on Plant Growth

0

6

34

12

0

10

8 7

5

9

12 9

How to Make a Graph 1. Use the same title as you did for your data

table. 2. The dependent variable goes on the

vertical axis; the independent variable goes on the horizontal axis.

3. Make a scale on each axis that is evenly spaced and include title and units.

4. Plot your points and connect them.

The Effects of Amount of Sunlight on Plant Growth

Plant Growth in cm

Hours of Sunlight per Day

0 20

3

4 10 1286

2

5

4

6

7

1

9

8

Drawing Conclusions A conclusion is a decision about the outcome of

an experiment You need to determine whether or not the

hypothesis has been supported Results may not be accepted if: 1. The data is based on small sample sizes 2. There was no control in the experiment 3. There was more than one variable used 4. The results are based on opinion 5. There is not enough evidence presented