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 true Not 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 variable The 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

Hours of Sunlight per Day 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. The Effect of Amount of Sunlight on Plant Growth Hours of Sunlight per Day Plant Growth in cm 2 1 4 3 6 5 8 7 10 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 9 8 7 Plant Growth in cm 6 5 4 3 2 1 2 4 6 8 10 12 Hours of Sunlight per Day

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