ENSI Lessons

The Checks Lab

Authors/Adaptors: Adapted by Steve Randak; version by Judy Loundagin

Each team has an envelope containing a series of bank checks. A few are removed at a time, and the team attempts each time to construct a plausible scenario that involves those checks. With each subsequent removal of checks, appropriate revision of the scenario is done. Final scenarios are compared by the class. Class discussion is designed to show how human values and biases influence observation and interpretation, even in science. This is one of the few nature-of-science lessons that has a biological connection. This is also one of the few lessons that model the "historical" sciences, e.g., geology, paleontology, astronomy, forensic science, and evolutionary studies (where one uses clues — rather than experimentation — to infer past events).

Lesson Concepts:

Grade Span: 5–12


Advance Preparation:

Time: One class period

Grouping: 3-4 per group

Teacher Background:
This exercise is designed to help students understand the idea that science is built on evidence that can be observed or deduced from the natural world. We gather evidence through the use of our senses. However, the evidence can be confusing, seemingly conflicting, and apparently random. Data is not always consistent nor even readable. Furthermore, all of the evidence may not be available. This is why scientific explanations are "tentative" explanations of natural phenomena.

In this simulation, there are several independent types of clues that may be used to develop an explanation (a hypothesis). This illustrates the concept that scientists use a variety of criteria to compare explanations and select the better ones. Scientists may even have to connect seemingly unrelated lines of evidence, always looking for patterns, to form tentative hypotheses. Evidence in science, as in this simulation, is not of equal value. Scientists must learn to discern between useful and useless data. In this simulation, the value of each check is affected by the order in which it is selected, and by the relative importance placed upon it by the various group members. Individuals with strongly held opinions or with strong personalities may have a major effect on their group's opinions. This aspect of the activity illustrates that human values, biases and experiences can deeply influence science.

This lab is open-ended. There is not enough information to say with certainty what the storyline is and each new check may create more questions than answers. This is a dynamic of both this lab and science. In addition, the participants should recognize that not everyone reaches the same conclusion when observing the same data, and why that is. Furthermore, this simulation encourages participants to equate the solving of a mystery with the search for scientific explanations. At the same time, this simulation reinforces the collaborative nature of science: scientists often work together to solve problems.

Finally, students may not notice this, but this "investigation" is not an experiment! Students seldom learn that great science can be done on events of the past, unobserved by anybody, and unrepeatable. Therefore, they must search for clues to explain a series of past events, looking for patterns and connections. This type of science is usually referred to as "historical science." When you are pointing this out (probably in post-lab discussion), ask students if they can think of any type of science that would be called "historical science." [Hopefully, students will think of forensic science (CSI), geology, paleontology, and astronomy. If not, give them hints!]

Teacher Resources:
Because this lesson provides an excellent opportunity to understand important elements of the Nature of Science, be sure to read Teaching the Nature of Science, with tips for presenting the ENSI NOS lessons for maximum effect and Dispelling some of the popular myths about science.
CONTEXT: This lesson is best used in your Nature of Science unit, preferably in the first 2-3 weeks of your course. If you used something else to convey the concepts listed above, then this lesson could be done later in the year as a little "something different" break, to reinforce those concepts.

Sample Scenario That Focuses on How This Lesson Models the Approach to "Historical" Sciences: See excellent article by Dr. Laura Henriques "Theoretically Speaking. "The Checks Lab is one of the few interactive lessons (along with various forensic lessons) that illustrates how science deals with problems of the past, events not experienced by available witnesses (sometimes called "historical" sciences, like astronomy, geology, paleontology and evolution science), nor open to repetition. This is in striking contrast to most investigative experiences found in textbooks and adhering to an overemphasis on "The Scientific Method," giving the impression that that is the only way science is done. Be sure to provide your students with this information while doing the Checks Lab (since this important process of science is usually ignored in textbooks).

Teaching Tips: See Teacher Background and Teacher Resources above.

Vocabulary: scenario, uncertainty, hypotheses/explanations, testing, historical science


  1. Arrange students into groups (four works well). Each group is given an envelope containing checks written by fictitious characters in a fictitious scenario (don't tell them this!). You can say something like "These envelopes contain a bunch of checks found in different drawers in the home of a family that no longer lives there." Tell students not to peek in the envelopes!

  2. Read the following introduction to your students:
    This activity is a simulation designed to help you experience how science works when figuring out past events, and that it is built on evidence that can be observed or inferred from clues in the natural world. However, this evidence can sometimes be confusing, seemingly conflicting, and apparently random. Furthermore, each new bit of evidence often creates more questions than it answers. The Checks Lab shows how scientific explanations are only tentative explanations, because new discoveries may show that previous explanations were incorrect. It also shows that some explanations are better than others, because they more logically explain all the data.

    No scientist works alone. This activity will demonstrate the value of collaboration within each group and with other groups in order to arrive at a reasonable explanation of the problem. There is at least one other characteristic of science that is not usually appreciated or realized by most people. See if you can figure it out while doing this lesson.

  3. Then have each team draw four checks from the envelope at random. Using the information on the checks, each group attempts to determine the circumstances that surrounded the writing of the checks. In other words, each group tries to come up with a storyline for the character(s) based on the information on the checks. This leads them to formulate their tentative explanation #1 for the checks — or a "storyline" that fits the checks. [This could be called a "hypothesis" if you like, but it's recommended to not do this — yet. Some students may recognize the "tentative explanation" as a hypothesis, but it's best to have them experience this explanation-building process before attaching a fancy word to it (hypothesizing). You can do this during class discussion (see their worksheets). Allow students to record this original tentative explanation.

  4. Then, instruct them to reach in the envelope without looking, and randomly select four more checks from the envelope. If you like, you can contrive a situation in which students are detectives using some checks found as partial evidence in some sort of crime; after a period of time, some more checks are found, perhaps in another drawer of the evacuated house. Observe the groups for insights as to how the new information affects their previous storyline. Once again, allow each group to work until it appears that most have exhausted their individual lines of thought, and have recorded their tentative explanation #2.

  5. Now each team should draw only two more checks and proceed as before, recording tentative explanation #3. After a few minutes, suggest that the different groups collaborate by sharing their information. The groups should realize that others may have one or two different pieces of data. Unused checks must stay in envelopes (in the real world, we never have all of the desired information).

  6. At the conclusion of this "share time", ask each group to select its strongest hypothesis (likeliest storyline) and record this as their final tentative explanation.

  7. After giving the groups time to formulate and record their final explanation, ask a group spokesperson to stand and report the group-selected explanation (storyline) to the class, so that all may hear different conclusions from similar data.

  8. Lead a follow-up discussion on the value of collaboration, tentativeness of scientific explanations, the effects of limited data, and the influence of personal biases and experiences on their ideas and ultimate selection of a most likely explanation. Even if scientists have a strong explanation of a natural phenomenon, they can never be absolutely sure that new data won't eventually appear and show the explanation to be wrong. You might also use this experience as a springboard to a closer look at some of the criteria scientists use to determine which storyline (explanation) is "best" (probably closest to reality).

  9. Also, again point out that this Checks Lab experience simulates the scientific process of investigating an unwitnessed historical event (or even pre-historical event), and tests hypotheses by looking for clues that could confirm or deny a given hypothesis, not by doing experiments.

  10. Allow students to answer the Discussion Questions, individually, or (probably better) collaboratively within each team. If time runs out, they can finish this as homework (if they have individual worksheets). If they do this, give all teams a chance to share answers and come up with preferred "Team" answers.

  11. When students have answered all (or most) of the questions, engage the class in sharing and discussing their answers, guiding their understanding toward the concepts generally indicated in Student Worksheet Key.

Additional Teaching Notes:
Although you could ask students to point out the elements of "The Scientific Method" which they are using in their development of a probable scenario suggested by the checks, I would make an even stronger point that they are not actually doing lab experiments to test their hypotheses (the usual criterion most people assume to be science). Instead, they are actually testing their ideas by looking for patterns of information in the checks in hand which are consistent with those ideas, thereby building a plausible, hopefully probable, story line which fits all the evidence. This is how forensic scientists (CSI, etc.) try to figure out how a crime was perpetrated, and who did it, something nobody living observed (or would confess to), can't really be repeated, and must be based solely on evidence found. This is also how scientists do much of their work in paleontology, astronomy, geology, and evolutionary biology, the "historical" sciences! Point out that there really is no one scientific method, but rather different methods, all designed to figure out the most accurate explanation that fits all the evidence. If you can get a copy of The American Biology Teacher (NABT journal) for August 2002, see the article on pages 427-432, by Robert Cooper: "Confronting Myths About Evolution and Scientific Methods," where this is ably discussed at length.

As for which scenario is "correct" or "best", emphasize that in science, we never know. Scientists use discriminating criteria to reach the "best" explanation for the moment, based on (and consistent with) existing data (evidence), and this may always be modified with new evidence; be sure to click to the "Fair Tests" link in item #1 under Extensions and Variations. Our experience is that, even though never proven (final), scientific findings tend to give us useful and reliable insights which have led to greater health, comfort, success, and the peace of mind that comes with understanding how our world works.

The Checks Lab is also an excellent way for students to experience the very real fact that even in science, cultural biases and experiences do influence interpretations (and even perceptions). Be sure to discuss this a bit, and be sure to start doing the "False Assumptions" lesson to further clarify how our common assumptions and "common sense" affect our judgments. Those False Assumptions sheets (display on overhead, without revealing the answers) make nice closing activities when you have a little extra time before the bell rings, and it's teaching them some important concepts, too.

Be sure to point out the social aspect of their efforts, just as we find in real science. Scientists typically collaborate, share ideas through conventions, meetings, and publications, much as your students were doing as they discussed the checks and recorded preliminary scenarios.

These are all the things most people fail to recognize as typical of science, so anytime you can do something to point them out (or even better, get them to point out), you will have clearly improved their science literacy.

Another element you might want to bring in at some point is a series of illusions. Science is often not just observation, or even common sense; perception is not always reality! Doesn't the earth seem flat outside? Doesn't the Sun seem to move across the sky? Don't species seem to stay the same, forever? Take a look at the ENSI page on illusions.

Finally, something else seldom explained for science students is that science is not democratic, and it's not supposed to be fair. Whatever reality is, it is, and in science, we are merely trying to find out what that reality is, consistent with observations, and trying to understand it. Our conclusions are not based on feelings, popularity, or logic, or certainly not what is currently politically correct! That's one reason why debate or voting are never appropriate means for getting answers in science. Presenting different scenarios, stories, "theories" or "hypotheses" in class, and letting students decide which one they think is best, is decidedly unscientific, especially if they are not given any objective criteria to apply to the selection process.

From the Checks Lab on the ENSI website.
Adapted from a Social Studies activity by Steve Randak.