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As I have mentioned in previous blogs, I try to set up an inquiry-based laboratory assessment for my students each semester. In these assessments I push my students to develop their own hypotheses and to create an experimental procedure to test it. I also expect my students to collect data, to analyze it and to write a reflective conclusion.

The assessment has several parts including my personal observations on how the students conduct themselves in the lab and a formal, typed, lab report.& What is the purpose of the lab report? My main goal for the lab reports is to have the students demonstrate their background knowledge about the topic and to make connections to what they observed in the lab to the rest of the world.

Whenever I expect my students to write formally, I find that my students benefit from graphic organizers to help organize and structure their ideas. I have created a lab organizer that I use as part of the preparation for the experiment and as a post lab reflection form. My students are then able to use the organizer as an outline for their formal report. Two areas that I focus on are writing the hypothesis and the conclusion sections of the lab report.

Writing a Hypothesis

Developmentally younger children need help to understand the difference between guessing logically versus wildly, so often a hypothesis is referred to as an “educated guess.” However at the high school level we should expect a more sophisticated understanding of hypotheses so the “educated guess” definition falls short. A hypothesis is a prediction about the effect an independent variable will have on a dependent variable. At secondary level students should be connecting their hypothesis to a reason for their prediction. Good scientists make connections to prior knowledge and a well written hypothesis also guides the design of the experiment.

Many students confuse the terms independent and dependent variables so I prefer to use manipulated and responding variables. I do teach my students both terms and I use the mnemonic MIX and DRY to help them remember the Manipulated or Independent variable goes on the X axis while the Dependent or Responding variable goes on the Y axis.

There are several ways to structure hypotheses. The most common approach I use is to use an if/then format written as:
If Manipulated Variable Does P, Then Responding Variable will Do Q because…

This format will not work in all cases but it emphasizes the cause and effect nature that underlines much of the scientific method. In order to understand why something happens, scientists try to isolate individual factors and manipulate them in experiments. An example of a hypothesis written in this style would be:
As the temperature of the snake’s cage decreases, the temperature of its body will also decrease. My reason for this prediction is that I noticed that reptiles don’t have fat or fur to insulate them.

One modification I can make for students that need more support is to use a fill-in the blank and circle the word format.

As the _____________________(MV) increases/decreases the ______________________(RV) will increase/decreases.

Writing the Conclusion

In the conclusion section of my formal lab reports I expect my students to tell me about connections they made between the experiment and their background knowledge. I also want my students to demonstrate a critical analysis of their results and determine whether the hypothesis was accepted or rejected. To help my students write this section of the lab report I developed a series of questions that I have them answer as preparation for writing the conclusion. I tied in the science process skills to the questions being asked to help my students also see that these are skills that good scientists use.

Observing: What was the most important information you gathered during the science experiment?

Ordering: Did you notice any patterns in your data? What kinds of patterns did you observe?

Comparing: How were the results of your experiment the same or different from the results of your classmates?

Communicating: How did you communicate what you learned? (Data table, Graphs, Records, Diagrams)

Relating: What did you learn from this experiment that was related to a fact you previously knew?

Applying: How might you use what you learned to invent something practical to help our world?

Most of my students want to check answers with each other so I give them permission to compare their data with other groups as long as they write about their comparison in the conclusion. Science doesn’t happen in a vacuum and most scientists should feel comfortable having their data verified by others. I also want to encourage appropriate collaboration between my students. Often the students have similar data but sometimes I have assigned different groups different materials so their data won’t match. I have found that most of the time when the data doesn’t match my students will start asking each other how they got that data and sometimes will request to redo portions of the lab to find out which group has the “right” data.

Over to You

How often do you have your students write formal lab reports? How do you structure your reports?

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