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.

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?

Scientific Method = Gathering Evidence

Last week, we learned that the Scientific Method is an organized method used by scientists to find and gather evidence (data) to support a claim (argument) about what the scientist observes.  There are many versions of the scientific method, but all versions of the scientific method involve trying to answer a specific question, and experimenting to find the answer.

The version of the scientific method that we will use in my class was given to me by my dear friend, Dr. OPHERC:

• Observation: The observation is simply any information gathered using the senses or an instrument.  A scientific investigation begins with an interesting observation in the world that generates questions that can be tested.

• Problem/Question: The problem/question is the specific question the scientist will attempt to answer through experimentation.

• Hypothesis: The hypothesis is the claim of the scientist, or an educated guess about the answer to the problem/question.  A hypothesis is based on sufficient observations, prior knowledge, and background research.  

• Experiment: The experiment is when the scientist actually tests his/her hypothesis for supporting evidence using detailed procedures, appropriate materials, and scientific measuring tools.  During the experiment, the scientist records all of his/her qualitative and quantitative observations.

• Results: The results are all of evidence (the qualitative and quantitative observations) gathered throughout the experiment.  The results are often displayed in tables, charts, and graphs for further studying. 

• Conclusion: The conclusion is the reasoning of the scientist that explains the meaning or significance of the results.  In the conclusion, the scientist links the evidence from the experiment back to the original claim (hypothesis).     

Scientific Explanation = Goal of a Scientist

During the first week of school, we learned that science is a way to develop explanations for what we observe, using the evidence we gather through our own experiments, and through the experiments of other scientists.  A scientific explanation, so to speak, is the scientific way of explaining what we observe in the world (and outside of the world, too!).  A scientific explanation is essentially a claim (about what a scientist observes/observed phenomena) that is supported with evidence and reasoning.  
The goal of a scientist is to develop scientific explanations to share with the scientific community, and the purpose scientific method is to gather the "evidence" component of the scientific explanation.  

But what is a claim?  What is evidence?  And what is reasoning?!  These components of a scientific explanation (C.E.R.) have been outlined below.

C.E.R. = Parts of a Scientific Explanation

• Claim: a conclusion that attempts to answer/address a testable scientific question. 
• Evidence: appropriate and sufficient data from an experiment, other scientists' experiments, reading material, and/or other observations that support the claim.  
• Reasoning: a justification that links the claim and evidence that incorporates appropriate and sufficient scientific principles; requires background research.  

Connecting the Scientific Method with C.E.R.

Last week, we performed an experiment to gather evidence in order to develop a scientific explanation. The question we addressed was, "What is the most common color in a 2.17 oz Original Fruit bag of Skittles?"

Below is an outline of how we gathered our evidence via the Dr. OPHERC.  We will use class 711's data for our example.

1.  The scientific method began with an observation.

Observation: There are five different colors in a bag of skittles - red, yellow, orange, green, purple.  Every time I eat a bag of skittles, the frequency (how many) of each color seems to be different.  

2.  This observation inspired, or led to, a question for investigation.

Problem/Question: What is the most common color in a 2.17 oz "Original Fruit" bag of Skittles?  

3.  We made a tentative claim (hypothesis) to test, based on our observations, background research, and prior knowledge.

Hypothesis: If purple is the most popular color of Skittles, then it will be the most common color in a 2.17 oz bag because the makers of Skittles will likely accommodate the preference of the consumers.  Furthermore, according to Skittles.com, green should make up 19.7% of a 2.17 oz bag, yellow should make up 19.5% of a 2.17 oz bag, orange should make up 20.2% of a 2.17 oz bag, red should make up 20% of a 2.17 oz bag, and purple should make up 20.6% of a 2.17 oz bag. 

4.  We then tested our hypothesis through an experiment to gather evidence.

Experimental Procedure:
1.  Open the bag of Skittles onto your sheet of paper towel.
2.  Group your Skittles according to color. 
3.  Count how many of each color are present in your group’s bag and record this info in table 1.   
4.  Analyze your data by creating a bar graph on Table 2.
5.  Make sure to label the graph showing colors and numbers of Skittles. 
6.  Form a conclusion.  State whether your hypothesis was correct or incorrect and why. 

5.  Next, we graphed all of our data (evidence).

Results:
Average number of red (class 711): 11.5 pieces
Average number of yellow (class 711): 13.3 pieces
Average number of orange (class 711): 10.2 pieces
Average number of green (class  711): 13.5 pieces
Average number of purple (class 711): 10.2 pieces

6.  We then made a conclusion by determining whether or not the evidence gathered supported our original claim.  The conclusion is essentially our reasoning.  The conclusion addresses our original claim (was it correct?  incorrect?), provides our evidence, and links our evidence back to our original claim.

Conclusion: My hypothesis was not supported through this experiment because I predicted that purple would be the most common color, and my results show that green is the most common color in this experiment.  The average total number of candies in class 711 was 58.6 pieces.  There was an average of 10.2 red candies, 13.3 yellow candies, 10.2 orange candies, 13.5 green candies, and 10.2 purple candies in a 2.17 oz bag.  Class 711's results were different from class 711, 714, 715, and 716. My next step is to average the data from all four classes.  Since every class has a different average frequency of colors, the results do not provide enough evidence to support or oppose my claim that purple is the most common color of skittles in a 2.17 oz bag.  Furthermore, since Skittles.com states that green should make up 19.7% of a 2.17 oz bag, yellow should make up 19.5% of a 2.17 oz bag, orange should make up 20.2% of a 2.17 oz bag, red should make up 20% of a 2.17 oz bag, and purple should make up 20.6% of a 2.17 oz bag, it is important that we increase our sample size in order to have a fair test.

Homework:

Answer the following questions in your science notebook.  Write the questions AND answer in complete sentences.

1.  Why do scientists use the scientific method?
2.  What is a scientific explanation according to this article?  Cite your evidence.
3.  How is the "reasoning" in a scientific explanation related to the claim and evidence?  Explain.
4.  According to this blog post, a claim is a conclusion that attempts to answer/address a testable scientific question.  What is another way to define claim?
5.  According to this blog post, evidence is appropriate and sufficient data from an experiment, other scientists' experiments, reading material, and/or other observations that support the claim.  What is another way to define evidence?
6.  Were we able to gather enough evidence through our Skittles experiment to support a claim that a particular color is the most common in a 2.17 oz bag of "Original Fruit" Skittles? Explain.
7.  Using the scientific method does not always provide the necessary evidence to support the claim (hypothesis) of the scientist.  What do you think a scientist should do in the case that the evidence does not support the claim (hypothesis)?  Explain what you think should be the next steps for the scientist.

Due: Monday, October 21, 2013.