Mayfly Data Variability and Analysis

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.