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Mayfly Data Variability and Analysis

Unit Plan: Stream EcologyLesson: 6 Time: 40 minute lesson Setting: Classroom
6-8Water & Watersheds
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Objectives

Students will understand how variation in data and sample size help us to make a claim. Students will learn to use "hedging language" in discussing results.

    Overview
    Rating:

    Main points of the lesson:

    • Variability is very important when looking at averages – scientists never look at an average without also looking at the scatter of data around that average.
    • The amount of scatter (or variability) will affect the confidence with which we can make a claim.
    • It is easier to predict outcomes when variability is low.
    • The higher the sample size the better we can see how much variability there actually is – sample size is also important when making a claim.
    • Real data is “MESSY”  but we prefer to call it  “INTERESTING”

    Materials

    • "Lesson 4 Worksheet Example" (see downloads below)
    • "Lesson 4 - Variability and Mayfly Data (powerpoint)" (see downloads below)
    • "April 2014 Mayfly Data Points" (see downloads below) - cut each row, so that each strip of paper will represent one data point
    • Large (poster size) version (laminated if possible) of the "Mayflies in Pools and Riffles ‐ April 2014" bar graph in Variability and Mayfly data powerpoint, without data points.  
    • dry erase marker or round sticky dots

    Engage 

    2014 data 

    • Present to students a bar graph of average mayfly data from pools and riffles from 2014.  (These should be big poster size versions of the graph “Pool and Riffles 2014” found in the PowerPoint “Variability and Mayfly Data” in the resources section. If possible, laminate the graph so students can draw on it and it can be used again.)  Discuss with students whether, based on averages they would answer the question “Is there a difference between Mayflies in pools and in riffles.”  How confident are they in their answer based on just the averages. 
    • Pass out strips of paper that have on data point from April 2014 for both pool and riffle and plot their point on the bar graph using dry erase markers.  (Use “April 2014 Mayfly Data Points”, cut spreadsheet into strips)  This will result in a bar graph that also has all the data points used to create the average.  This allows students to visualize the scatter of the points around the mean. 

    The final graph with all data points should look like this: 

    • Discuss with student how their answer to the question “Is there a difference between pools and riffles” might change after each data point is added.
    • Discuss with students how scientists always use the scatter (variability) around the average to draw conclusions and discuss their data.  They never look at just averages. 
    • Often times this scatter helps us to identify outliers (data points that are very different from the rest).
    • Some people refer to data that has a lot of variability as “messy” - in fact real ecological data is usually highly variable.  Encourage students to think of it as “interesting” instead of “messy”.

     

    Explore

    Part 1 – This year’s data

    • Now pass out worksheets prepared ahead of time that have the data they collected on their field trip and graphs of the average number of mayflies in pools and riffles plotted on a bar graph (see example worksheet for lesson 4).
    • Have students plot their data on the bar graphs to more easily visualize the scatter of data.
    • Discuss with students their results.  Can we answer our question “Is there a difference between pools and riffles?”  How confident are we in our answer based on our data? 

     

    Part 2 – Talking and writing about our results

    • Use PowerPoint to introduce the term “Hedging Language”.  Discuss how scientist use this type of language to discuss their results.
    • In writing hedging language is the use of cautious language to make a noncommittal or vague statement.
    • Show students the slide of an example graphs (Dogs and cats sleeping) and the caption that describes the graph using hedging language.

     

    • Have them write a caption for the graph of their data using hedging language.
    • To help them determine confidence in their claim have them predict where a data point would be if another kick sample was taken in both pools and riffles.  The easier it is to make the prediction the more confidence they should have in their claim (and their data).
    • Students should try to answer these questions using their graphs and data:
        1. If someone asked you where they could find mayflies in the stream what would you say?
        2. How confident would you be in your response?

     

    Evaluate

    The captions students write for their graphs can be used as a formative assessment to gauge understanding of the topic. 

    Extend

    Part 1

    Provide student with mayfly data collected at the Cary Institute on 4/22/15 and 4/23/15 (below).  Have them find average for pools and riffles and plot on graph paper.  Then have them add data points to help them see the scatter of data now that they have more data. 

    Have students write a caption for the graph of their mayfly data using hedging language.  Lower level students might need help with this and the exercise can be done together as a class or in groups if needed. 


    School

    Date

    Habitat

    Sample

    # of Mayfly Larvae

    Average

    Oakwood

    4/22/2015

    Riffle

    Kick 1

    233

     

    Oakwood

    4/22/2015

    Riffle

    Kick 2

    60

     

    Oakwood

    4/22/2015

    Riffle

    Kick 3

    86

     

    Oakwood

    4/22/2015

    Pool

    Kick 1

    27

     

    Oakwood

    4/22/2015

    Pool

    Kick 2

    17

     

    Oakwood

    4/22/2015

    Pool

    Kick 3

    109

     

    Homeschool2

    4/23/2015

    Riffle

    Kick 1

    143

     

    Homeschool2

    4/23/2015

    Riffle

    Kick 2

    216

     

    Homeschool2

    4/23/2015

    Riffle

    Kick 3

    270

     

    Homeschool2

    4/23/2015

    Pool

    Kick 1

    2

     

    Homeschool2

    4/23/2015

    Pool

    Kick 2

    23

     

    Homeschool2

    4/23/2015

    Pool

    Kick 3

    2

     

    Part 2

    1. Ask the class the question “Is there a difference between the height of boys and girls in ____ grade”.  
    2. Randomly select three boys and three girls and have them stand in the front of the room. 
    3. Without actually measuring the height of each student, have the class answer the question based on their observations of the students at the front of the room. 
    4. One by one ask another boy and girl to join the group at the front.  After each new student goes to the front of the room ask if the answer to our question changes.  Discuss how our confidence in our answer gets stronger the more students there are.  Do this until all the students are lined up at the front of the class. 
    5. Pull one girl out and one boy out of the line that appear to be “average” height for the class.  Discuss with students how they would have answered the question if they only saw these two “average” students.  How confident are they in their answer, considering they know that there are some students that are shorter and some that are taller than the average student. 
    6. Explain that this is how scientists look at data.  They never look at just averages, but always look how the data is scattered around that average.  This scatter is called variability.

     

    Examples of hedging language:

     

    Verbs

    Adverbs

    Adjectives

    Nouns

    Phrases

    seem

    • often

    certain

    possibility

    It could be the case that

    tend

    sometimes

    clear

    assumption

    It might suggest that

    think

    usually

    probable

    probability

    Somewhat of a pattern

    believe

    probably

    possible

     

    Very little difference

    suggest

    possibly

      

    a bit less

    might

    perhaps

      

    Appear to be

    could

       

    Look like

     

    Lesson Files

    pdf
    April 2014 Mayfly Data Points
    pdf
    Example worksheet for Lesson 4
    pdf
    Variability and Mayfly data (Powerpoint)

    Benchmarks for Science Literacy

    2A Patterns and Relationships, 2B Mathematics, Science and Technology, 9D Uncertainty

    NYS Standards

    MST 1 - Mathematical analysis, scientific inquiry, and engineering design, MST 3- Mathematics in real-world settings, ELA 1- Language to collect and interpret information and understand generalizations
    Next Generation Science Standards

    Science and Engineering Practices

    Analyzing and interpreting data, Engaging in argument from evidence, Obtaining, evaluating, and communicating information

    Developed and written by Jen Rubbo and Andrea Caruso

    Lesson was adapted from ideas presented in:
    Bowen and Bartley. The Basics of Data Literacy, Helping your Students (and You!) Make Sense of Data, 2014. NSTA Press