Steps of the Scientific Method

Steps of the Scientific Method Science 8

Overview • What is the scientific method? • It’s a process of experimentation that allows us to explore observations (what we see) and answer questions • It’s a way for us to analyze cause and effect relationships in nature • An experiment is designed so that changes to ONE item cause something ELSE to vary in a predictable way

How you will use it… • For your science fair project, the scientific method will help YOU: • Focus on your science fair project question • Construct a hypothesis • Design and carry-out an experiment • Analyze the results of your experiment • Decide whether your hypothesis was supported or not!

T H E S T E P S

Step 1: Ask a Question • The method starts when you ask a question about something you observe… • How, What, When, Which, Who, Why, Where? • For the scientific method to answer the question, it should be about something that you can MEASURE (preferably with a number)

Helpful Hint… • It’s a good idea to choose a science fair topic that you are interested in or curious about. • That way, you will have more questions and you will have fun carrying out your project!

Step 2: Do Background Research • Do not start your science fair project blindly! • Be a savvy scientist and use the internet and library to research… • Information on your topic • The best ways to do things • Mistakes that you don’t want to repeat

Important Note! • When you are doing your background research, make sure you WRITE DOWN ALL REFERENCES that you use! • You will need them later for you bibliography!

Step 3: Construct a Hypothesis A what?! A hypothesis is an educated guess about how things are going to work: “If ______ [I do this], then _______ [this] will happen.” A hypothesis should be constructed in a way to help you answer your original question.

A testable hypothesis • A hypothesis should be worded so that it can be tested in your experiment. • You need to be able to measure “what you do” and “what will happen.” • There are two important terms we must understand: 1) Independent Variable 2) Dependent Variable

Variables • In any experiment, we can really only test one thing at a time. So we try to control all the variables except one that we will change. • Independent variable = the variable that you change during the experiment • Dependent variable = the variable that you observe changes in (depends on the independent variable)

Back to the Hypothesis The hypothesis should be a statement that relates your dependent and independent variables in a way that can be tested or measured: “If a particular independent variable is changed, then there will also be a change in a certain dependent variable.”

Hypotheses - Examples • "If a plant receives fertilizer, then it will grow to be bigger than a plant that does not receive fertilizer.” • Independent variable = having fertilizer • Dependent variable = size of the plant • “If 2% milk is left at room temperature, bacterial growth will occur at a faster rate than in skim milk left under the same conditions.” • Independent variable = amount of fat in milk • Dependent variable = rate of bacterial growth

Step 4: The Experiment • Your experiment tests whether your hypothesis is true or false. • It is important that the test is fair: • You change ONLY ONE variable at a time, keeping all others the same (constant). • You should repeat your experiment several times to make sure your results weren’t just an accident. • Good precision = at least 3 trials

# of Trials  More Consistency • If your experiment involves plants, you should do the experiment on at least 3 plants in separate pots. • If you are doing an experiment that involves surveying or testing different groups, you will want to test or survey a sufficient number of participants to ensure that your results are reliable.

Experimental Procedure A good experiment… • follows a step-by-step procedure (like a recipe) • Should be easily duplicated by another scientist (your procedure is thorough!) • Has controlled variables that do not change during the experiment and stay the same in each trial

Control Group Some experiments have a control group: • This means that in one trial, you do NOT change the independent variable (leave it in its natural state) • Most experiments have this (some do not). See your teacher if you are unsure.

Step 5: Analyze Your Data • When your experiment is complete, you then collect your measurements (data) and see if your hypothesis is true or false! Let’s look at HOW to do this…

How to Analyze Data • Review your data first • Is it complete? • Do I have enough trials? Or enough people? • Did I make any mistakes? • Graph your data • Construct a graph of your measurements. The independent variable goes on the x-axis and the dependent variable on the y-axis • Calculate an average for the different trials • See the example next…

Calculating an Average • This is done by • adding your measurements of the dependent variable together • then dividing by the total number of trials Example: You measured the size that a plant grew when you added 10mL of fertilizer. You did 4 trials (repeated experiment 4x): Average Plant Growth = (1.32cm + 1.41cm + 1.36cm + 1.38cm) ÷ 4 = 1.37cm • Avg = (trial 1 + trial 2 + trial 3…) ÷ (total # of trials)

Step 6: Draw Conclusions After you have analyzed your data, you can make some conclusions: • Summarize your results in a few sentences • State whether your results support or contradict your hypothesis. • Evaluate your experimental procedure (was it successful, effective?) • Suggest changes in the procedure and/or possibilities for further study.

Step 7: Report Results • Finally you will communicate your results to others in a final report and a display board. • Professional scientists do almost the same thing by publishing their results in a scientific journal. And that is the final step in the scientific method!

Get Started and Have Fun! Very Helpful Reference: http://www.sciencebuddies.org/mentoring/project_scientific_method.shtml

Steps of the Scientific Method