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Scientific Questions = Testable Questions

10/30/2013

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Scientific Questions = Testable Questions

The scientific method (Dr. OPHERC) is a way to gather evidence in order to develop a scientific explanation of phenomena.  After making interesting observations (O), we identify problems (P) and questions for investigation.  However, it is important that the questions we ask are  "testable".  Without a testable question to start our investigation, we won't be able to gather meaningful evidence.

What is a testable question?

A testable question asks something that can be measured and observed (phenomena) through experimentation.  In other words, a testable question can only be answered by gathering evidence.  If your question does not require collecting data (qualitative and quantitative observations), then your question is NOT "testable".

Another way to think about is in terms of a controlled experiment.  A testable question asks how one change (independent variable) has an effect on something else (dependent variable).

Testable questions examine cause and effect relationships.  In other words, testable questions look into how an independent variable (IV) affects a dependent variable (DV).

Below are some example testable question formats:
  • How does            (IV)           affect          (DV)         ?
  • What is the effect of            (IV)            on            (DV)          ?
  • What effect does            (IV)            have on            (DV)          ?

Testable questions are not related to personal preference, moral values, the supernatural, or things that cannot be measured.  Just remember: Testable questions do not ask about things that are NOT considered to be phenomena!
How do you turn a topic into a testable question?

Now it is time that we learn how to develop our own testable questions so that we can begin designing our own controlled experiments!  It is important that we choose topics that are meaningful and of interest to us. Therefore, the next question is, how do we take a topic (that interests us) and turn it into a testable question for investigation?

1.  First, make two lists.
  • List everything you can measure about your topic of interest.
  • List everything that you can change/treat differently to your topic of interest.

Example Topic: Tomato Plants
  • List everything you can measure about the tomato plant (DV): height of plant, number of tomatoes, color of tomatoes, water content of tomatoes, number of leaves, mass of tomatoes, density of tomatoes, depth of the roots, circumference of tomato, pH of the tomatoes, etc.
  • List everything that you can change/treat differently to your tomato plant (IV): amount of sunshine, type of light, amount of soil, type of soil, amount of compost, type of compost, species of tomato plant, amount of water, temperature, humidity, number of seeds in the pot, type of pot, pH of the soil, pH of the water, type of water, etc.

The first list are possible dependent variables.  The second list are possible independent variables.

2.  Next, pick one item from each list that interests you most.
You are essentially picking one dependent variable and one independent variable.

Example:
  • Water content of tomatoes = Dependent Variable
  • Amount of water = Independent Variable

3.  Finally, choose an appropriate testable question format and fill in the blanks with the appropriate variables.
  • How does            (IV)           affect          (DV)         ?
  • What is the effect of            (IV)            on            (DV)          ?
  • What effect does             (IV)               have on           (DV)             ?

Example:
What is the effect of the amount of water given to a tomato plant on the water content of tomatoes?
Watch the video below on how to write testable scientific questions for investigation!  
In-Class Activity
Answer the questions below using information from the blog post and video.  Write the question and answer in complete sentences.

1.  What is a testable question? (highlight your definition in BLUE)
2.  What is NOT a testable question?
3.  What are the two parts of a controlled experiment that are in every testable question?
4.  What are the 3 steps to turning a topic into a testable question?
5.  Write 3 more testable questions about the tomato plant by following the steps in question #4.
6.  Follow the steps for turning the topic "Cafeteria Pizza at MS 88" into a testable question.  Make sure to outline each of the 3 steps to get full credit.  
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Controlled Experiments

10/22/2013

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What is a controlled experiment?

A controlled experiment is an experiment that is conducted under a setting that is “controlled” by the scientist with the least possible influence from outside factors.  A controlled experiment compares an experimental group with a control group in the exact same conditions with the one exception of a special/different treatment given to the experimental group. 

The control group represents the "normal", "standard" or untreated condition.  The experimental group is the one part of the experiment that is changed/manipulated (given different treatment).  The constants are everything else you keep the same to ensure a fair test.

Francesco Redi's Controlled Experiment: Do maggots (young flies) come from rotting meat?

To better understand controlled experiments, let's look at Francesco Redi's famous controlled experiment on maggots and meat as an example.  Francesco wanted to find the answer to the question, "Do maggots (flies) come from rotting meat?".  This may seem like a really silly question, but in Francesco Redi's day (1600s), people actually believed that flies and maggots were generated spontaneously from meat.   Take a look at Redi's experiment below.
Picture
What conditions did Francesco keep the same?  What was the one special/different treatment given to the meat?  
Louis Pasteur's Controlled Experiment: Can microorganisms (germs) generate spontaneously?

Louis Pasteur also conducted a famous controlled experiment.  His experiment addressed the question, "Can microorganisms (germs) generate spontaneously?"  For hundreds of years before Louis Pasteur, scientists believed that microorganisms (living things too small to see with the naked eye) came from thin air.  Below is Pasteur's experiment.
Picture
What conditions did Pasteur keep the same?  What was the one special/different treatment given to the flasks?  
A controlled experiment is a "fair" test
A controlled experiment is usually the fairest and most accurate way for a scientist to gather evidence to test a claim (hypothesis). Therefore, we will be using controlled experiments, like Francesco Redi and Louis Pasteur, in science class this year as we develop scientific explanations of phenomena that interest us.

A controlled experiment can be replicated
Another important thing to note about controlled experiments is that they are super easy to replicate (copy).  Therefore, any scientist should be able to gather the same evidence and results when conducting the same experiment.  In other words, if you performed Francesco Redi's famous experiment from the 17th century today, you would get the exact same results (replicated results)!


Limitations of a controlled experiment
However, keep in mind that controlled experiments have their limitations.  First of all, not every experiment can be controlled in a laboratory setting.  For example, if you want to study things in nature, such as how specific plants and animals interact in the rain forest, there are many factors that you would not (and should not) be able to control/change.  Furthermore, controlled experiments do not necessarily represent real-world conditions, and can therefore create unrealistic results.  For example, if a scientist is able to prove the effectiveness of a new drug (medicine) in a controlled laboratory setting, this does not necessarily mean that the drug will be as effective among people who have very different diets and live in very different environments.
In-Class Activity

Perform Redi and Pasteur's famous controlled experiments here!  Then answer the questions below. 

1.  What is a controlled experiment?

2.  What are the two "groups" in a controlled experiment?
3.  What is a control group?
4.  What are constants?
5.  Identify the experimental and control group in Francesco Redi's controlled experiment.
6.  How was Louis Pasteur able to gather evidence to prove that microorganisms do not generate spontaneously?  Explain.  If you need help, review Louis Pasteur's experiment here.
7.  Why do you think it is important to keep all conditions in a controlled experiment the same except the one special/different treatment?
8.  Why is it important that you can "replicate" a controlled experiment?
9.  What is one limitation of a controlled experiment?
Homework

Watch the video below on a controlled experiment studying the effect of ozone on plants  Then answer the questions in your science notebook in complete sentences.

1.  What was the question the scientists were trying to answer through this controlled experiment?
2.  How were all of the plants treated the same?
3.  What is a variable?
4.  What is the variable (one thing changed) in this experiment?
5.  What was the control/control group in this experiment?
6.  What is a control/control group?
7.  What do the scientists measure/record everyday in this experiment?
8.  Why do you think it is important that scientists only test one variable in an experiment?
Extra Credit:

Watch the video of how students set up a controlled experiment to investigate the effect of mirrors on dolphin behavior: http://vitalny.pbslearningmedia.org/resource/737ed8f2-10bb-484e-9b75-e3f19a91f3a4/dolphin-dive-05-test/
Then answer the questions below.

1.  What was the control test/group in the dolphin experiment?
2.  What was the experimental group in the dolphin experiment?
3.  How do you think the students could have improved their experiment?
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