EnvironMentors

Experimental DesignWorkshop

The Scientific Method

1. Identify a Problem/Ask a Question

2. Background Research

3. Form a Hypothesis

4. Design an Experiment

5. Data Collection and Analysis

6. Draw a Conclusion

7. Communicate your Results

Identify a Problem/Ask a Question

• Your Research Question is the most important part of the Scientific Method

• Choose a problem that interests YOU

• In EnvironMentors, you used the Mind Mapping technique to identify the environmental issue most important to you

Background Research

• Learn more about yourproblem

• Review previous work inyour area and talk to experts

• In EnvironMentors, you did Background Research when you did your Literature Review and your Expert Interview

Form a Hypothesis

• Based on your Background Research, make an educated guess to answer your Research Question

• Your hypothesis should be testable

• You developed your hypothesis at the end of your Background Research Paper.

Design an Experiment

• What data will you need to collect to test your hypothesis?

• What variable will you change?

• Identify a study site or sites, choose dates and times for your experiment, and create a list of necessary materials.

• Describe your experimental method.

Step-By-Step Process

• Identify your Independent, Dependant, and Control Variables.

• Develop a procedure and Methodology for measuring your changes/results.

• Set up at least 3 trials (times you perform you experiment) for accurate results.

• Every time you run your experiment or check your results, make sure that you Control Group is remaining constant.

• Be sure to follow your measuring steps every time you check your results.

• Before you begin your experiment, write out a DETAILED, step-by-step list of all the procedures for your experiment.

Materials

• At a simplified level, you can think of your Experimental Method as being like a recipe in a cookbook. Your procedure is like the instructions for how to bake a cake. The instructions will include things like the order to mix the ingredients, and the temperature to set the oven. Your Materials List is like the list of ingredients. A recipe that lists only flour, sugar and eggs would be nearly useless; you would need to know how much flour and sugar and how many eggs in order to bake a good cake.

• Make sure you include everything you will need for your experiment in your materials list, including notebook and pen for recording.

What Materials do you think he needs for this experiment?

VariablesAn experiment generally has three types: independent, dependent and

controlled. When choosing your variables, keep in mind that good variables are usually those that you can measure with a number (e.g., concentrations of pollutants, time of day, temperature) or

observe objectively (e.g., colors). Subjective qualities, like whether noise pollution makes local birds happy or sad, are not appropriate

variables.• The independent variable is the one that you, as the scientist,

change or manipulate. Your experiment should have only one independent variable. For your EnvironMentors project, possible independent variables could be time (e.g., testing the amount of pesticides in the water at the same site on different days) or location (e.g., measuring noise pollution at different locations at the same time of day). Time and location are just two examples of independent variables. You and your mentor should work together to determine the best independent variable for your project.

Variables

• The dependent variable changes in a consistent manner in response to changes you make in the independent variable. In the examples above which used time and location as the independent variables, the dependent variables would be the amount of pesticides in the water, and the amount of noise pollution, respectively. Whereas there should only be one independent variable, the number of dependent variables can vary. For instance, if you were investigating water quality at the same site on different days, your independent variable would be time, and each different pesticide concentration you measure in the water would be a different dependent variable.

Variables• The controlled variables are those that you try to keep constant

throughout your experiment. These are all variables that might affect your dependent variable. If you were measuring the concentrations of pesticides in water on different days, you would want to make sure that things like the weather and outside temperature remain relatively constant. You should keep track of your controlled variables as carefully as your other variables. Remember that it is important to try to keep your controlled variables as constant as possible. For instance, if you measured the noise pollution at two different traffic intersections in your city (independent variable = location; dependent variable = noise pollution) but made your measurements at different times of day, you wouldn’t be able to tell if changes in the amount of noise pollution were due to the different location or the different time of day. Most experiments will have more than one controlled variable.

Data Collection and Analysis

• For EnvironMentors, you’ll need to collect at least 3 sets of data

• When you are collecting your data you must be Accurate, Consistent, and Persistent.

• Analyze your data:– Find the mean, median, mode– Use graphs to communicate your results

Mean, Median, Mode

24, 13, 45, 24, 67, 78, 85

Mean (or average):(13+24+24+45+67+78+85)/7 = 48Median (the value in the middle):

45Mode (the value that occurs the most):

24

Bar Graph

• Bar charts are used to show relationships between groups. The values being compared do not need to affect each other. This type of graph is an easy way to show large differences.

• Example 1: Using a bar chart to show the differences in rates of water percolation through different types of soil.

Trial 1 Trial 2 Trial 3 Mean Soil type

Time (seconds)

Sand 40 41 45 42

Clay 55 60 57 57.3

Potting Soil 21 23 27 23.7

Control 8 5 4 5.7

Comparing Water Percolation Through Different Soil Types

0

10

20

30

40

50

60

70

Sand Clay Soil Control

Soil Type

Perc

olat

ion

Tim

e (s

ec.)

Line Graphs

• Line graphs are used to show how changes in one variable affect changes in another variable. It is very common to create a line graph by plotting your independent variable on the x-axis (bottom) and your dependent variable on the y-axis (left). Line graphs can also be used to show how data change over time.

• Example 2: Using a line chart to show the changes in river flowrate over time.

January 1 February 1 March 1 River

Flowrate (cubic feet per second)

Klamath River 375,000 327,000 320,000

Eel River 647,000 542,000 498,000

Trinity River 166,000 161,000 131,000

Mad River 62,000 57,000 38,000

Comparing River Flowrates

0.0E+00

1.0E+05

2.0E+05

3.0E+05

4.0E+05

5.0E+05

6.0E+05

7.0E+05

1-Jan 1-Feb 1-Mar

Flow

rate

(cu.

ft/s

ec)

Klamath Eel Trinity Mad

Pie Chart

• Pie charts are used to show how a value for a part of something relates to the whole. This type of graph is an easy way to show percentages.

• Example 3: Using a pie chart to show the different bird species observed on the Outer Banks of North Carolina.

12.3, 18%

18.3, 28%

15.3, 23%

9.3, 14%

11.6, 17%Pelican

Sanderling

Great Egret

Snowy Egret

Other

Day 1 Day 2 Day 3 Mean Type of Bird

Number of birds

Pelican 10 12 15 12.3/66.8= 18%

Sanderling 20 18 17 18.3/66.8= 27%

Great Egret 15 16 15 15.3/66.8= 23%

Snowy Egret 9 8 11 9.3/66.8= 14%

Other 12 10 13 11.6/66.8= 17%

Draw a Conclusion

• What does your data mean?

• Does it disprove your hypothesis or support it?

• What other experiments can you do to learn more?

• What would you do different next time?

Communicate your Results

• Write your Final Report, and present your results at the EnvironMentors Fair.