Today, my Human Biology class did a respiration lab on tidal volume. Here is my lab rubric. The first step is to determine either a hypothesis or the purpose of the lab. Most labs have a purpose rather than a hypothesis. The purpose of the Tidal Volume lab was to understand tidal volume.
Next, the kids write the materials using complete sentences. For example, "The materials include the following: one milk jug, two meters of aquarium tubing, one milk jug, one 1000 mL beaker, and one bucket.
The methods follow. The first step is to fill a bucket about half-full. Next one fills one gallon milk jug with water and caps the jug. After filling the jug, the student inverts the jug into the bucket of water, removes the cap, and inserts the plastic tubing. The students work in pairs; one student is responsible for removing the cap and holding both the tubing in place and the jug up-ended in the bucket without cutting off the tubing. The next step is to take a deep breath and inspire into the jug via the tubing. Next, one removes the jug from the bucket and measures the remaining water. It is necessary to measure the amount of water in the full jug initially, also. It measures slightly more than one gallon. The results represent three trials for each student and tabulated.
The data table for this lab has results for four students: 600 mL, 550 ml, 500 mL, 300 mL, 750 mL, etc.
Data: Tidal Volume
Trial Volume (mL)
1 600
2 550
3 500
The results are next. The results for this lab should include the mean, median, and mode.
The next section is discussion. In this section the student explains possible sources of error. For example, it may be difficult to regulate a deep breath.
The last section is the conclusion. An acceptable conclusion is, "More study is indicated." For most experiments, the class size is too small to make broad statements about the validity of the results. For example, the average tidal volume for a healthy, young, male adult is 500 mL. Today, we took about 12 trials using four students. There is insufficient data or trials to draw meaningful conclusions.
Lab reports are good examples of technical report writing. My students use complete sentences using the third person, present tense, active voice, and indicative mood. Sometimes, the passive voice (i.e. The results are repeated.) may be used.
My students rewrite their lab reports three or four times. I require citations if the lab requires background information. My husband assigns several formal lab reports in Physics. I assign two or three formal lab reports in Chemistry. I may insist on a data table or summary statistics. Two or three times for each course, my students must write and correct formal lab reports. The Human Biology class met weekly for two hours and began in May, met over the summer, and is concluding the end of September. The class was treated as a one semester elective. The tidal volume lab will probably be the only formal lab report.
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