*This is a modified version of the original Data Nugget that has been designed to be used on the DataClassroom web-app. The original pencil and paper activity can be found here on the Data Nuggets website

Featured scientist: Leila Desotelle from Michigan State University

Background

Ever since she was a kid, rivers have fascinated Leila. One of her hobbies is to kayak and canoe down the Kalamazoo River in Michigan, near where she lives. For her work, she researches all the living things in the river and how humans affect them. She is especially interested in changes in the river food web, caused by humans building dams along the river, and an oil spill in 2010.

Leila knows there is a lot more in river water than what meets the eye! As the river flows, it picks up bits of dead plants, single-celled algae, and other living and nonliving particles from the bottom of the river. The mix of all these particles is called total suspended solids (TSS) because these particles are suspended in the river water as it flows. The food web in the Kalamazoo River depends on the particles that are floating in the water. Invertebrates eat decomposing leaves and algae, and fish eat the invertebrates. 

As you float down the river, particles settle to the river bottom and new ones are picked up. The amount of suspended solids in a river is influenced by how fast the water in the river is flowing. The faster the water flows, the more particles are picked up and carried down the river. The slower the water flows, the more particles will settle to the bottom. Discharge is a measure of how fast water is flowing. You can think about discharge as the number of cubes (one foot on each side) filled with water that pass by a point every second. During certain times of the year, water flows faster and there is more discharge. In spring, when the snow starts melting, a lot of water drains from the land into the river. There also tends to be a lot more rain in the fall. Things humans build on the river can also affect discharge. For example, we build dams to generate hydroelectric power by capturing the energy from flowing water. Dams slow the flow of river water, and therefore they may cause some of the suspended solids to settle out of the water and onto the bottom of the river. 

Scientific Questions:  (1) How does the dam influence the amount of total suspended solids present in the river water? (2) Does this effect differ depending on time of year?

Scientific Data:

Leila wanted to test how a dam that was built on the Kalamazoo River influenced total suspended solids. If the dam is reducing the amount of total suspended solids, it could have negative effects on the food chain. She was also curious to see if the dam has different effects depending on the time of year. On eight different days from May to October in 2009, Leila measured total suspended solids at two locations along river. She collected water samples upstream of the dam, before the water enters the reservoir, and samples downstream after the water has been in the reservoir and passed over the dam. She also measured discharge downstream of the dam.

1. What is the hypothesis? Find the hypothesis in the Research Background and copy/paste it below:  (A hypothesis is a proposed explanation for an observation, which can then be tested with experimentation or other types of studies.) 

2. Click on the graph tab, and explore the available variables.  What data will you graph to answer the scientific question #1?

Independent variable:
Dependent variable:

3. Create your graph of your data for scientific question #1 and paste it below:

4. To find the mean of the data, add descriptive stats, select SEM, and paste it below:

5. Identify any changes, trends, or differences you see in your graph

Graph for Scientific Question 2:

6.  Click on the graph tab, and explore the available variables.  What data will you graph to answer the scientific question #2?
Independent variable:  
Dependent variable:

7. Create the graph of your data for scientific question #2 and paste it below (you may need to turn off descriptive stats from your previous graph):

8.  Identify any changes, trends, or differences you see in your graph.

Interpret the Data:

9. Make a claim that answers the scientific question.

10. What evidence was used to write your claim? Reference specific parts of the tables or graph.

11. Explain your reasoning and why the evidence supports your claim.

12. ​​What do the data from this study tell us about Leila’s hypothesis?

13. What conclusions can we draw from Leila’s research? Discuss the limitations on what we can say, based on these data. What future data could be collected to address these limitations?

Your next steps as a scientist:

14. Science is an ongoing process. What new question(s) should be investigated to build on Leilei’s research? What future data should be collected to answer your question(s)?

15.  Scientific Question 1:  We want to find out of the numbers from the graph you created for #4 are actually different enough to be meaningful! Reset your graph to those variables, and run a graph-driven hypothesis test and list the t-score and p-value below:

T-score:
P-value:

16.  Which value (the t-score or p-value) tells us if upstream and downstream are statistically significant differences?  What is the big takeaway from that statistical test? 

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