Handling Discrepancies



A revised version of an individual lesson plan developed by

William Leacock, W.C. Mepham High School, Bellemore, Long Island, NY

Courses for Which the Lesson is Intended:

Physics classes.

Types of Teaching/Learning Activities Employed in this Lesson:

Working in groups of 2 or 3, students perform a simple laboratory experiment with resistors.

Equipment has been altered in a manner that is likely to induce students to report what they expect

to observe, rather than what they actually observe.

After performing the experiment, the teacher leads a class discussion of the ethical issues it raises.

Category that Best Describes this Lesson:

Behavior of students.


Ethics/Values Issues Raised by this Lesson:

Honesty in interpreting and reporting data acquired in experimental procedures.

Lesson Plan

1. The teacher hands out Laboratory 26--Series Circuit (attached) and explains the procedure to the students.

2. Students are divided into groups of 2 or 3, depending on available equipment and the total number of students.

3. The teacher passes out the materials. However, a 20 ohm resistor is altered to look like a 10 ohm resistor.

4. Students are allowed the remainder of the period to complete the lab, with lab reports turned in at the end of the period.

5. When the reports are collected, students are asked to place their cover sheets last so that their names are hidden.

6. Between the first period and the second the teacher makes two columns on the chalkboard, one entitled altered, the other unaltered.

7. Without looking at student names, the teacher reviews the lab reports and records on the chalkboard the number of students who altered their data to conform with what would be expected with a 10 ohm resistor and the number who did not.

8. As the next period begins, the teacher explains to the class that one resistor was incorrectly marked as 10 ohms when it really was a 20 ohm resistor. Then the altered and unaltered columns on the chalkboard are explained (including the fact that no names are recorded).

9. The teacher invites students to discuss what has happened and its possible ethical implications. Questions such as the following could be asked:

  • There was a discrepancy in this experiment. Is it unethical to alter your data in order to accommodate a discrepancy like this? Why or why not?
  • What about scientists engaged in large scale research projects? Is it unethical for them to alter their data in order to make the results match their expectations? Why or why not?
  • What kinds of factors might lead science students and scientists to alter their original answers? Are these simply excuses, or rationalizations? Or do you think that sometimes they actually justify altering data?
  • What do you think is most needed in order to minimize unjustified data alteration by science students? By scientists?

  • Discussion

    This lesson clearly raises issues about honesty in interpreting and reporting data acquired in experimental procedures. Although there may be cases in which there is some uncertainty about how one's data can be reasonably and fairly presented, this is not such a case; and there should be little doubt in student's minds that altering the data to conform with what they would expect from a 10 ohm resistor is dishonest reporting. What may be less certain to them is whether it is ethically wrong for them to alter the data. Most students realize that cheating commonly occurs, and they may wonder why they shouldn't cheat if cheating is so common. Discussing what happens when scientists cheat can help stimulate a discussion of the seriousness of cheating in a science lab.

    Some students may reply that scientists cheating is different than students cheating. The consequences of scientists cheating can be very serious for others (e.g., resulting in doctors and their patients assuming that prescription drugs are safe when the data supporting this has actually been altered). But, students might say, at most, students hurt only themselves when they cheat; besides there are special pressures to do well as students in order to get into good colleges: once the pressure is off, and when the stakes for others are higher, they won't cheat.

    Time permitting, the class could be shown the NOVA program "Do Scientists Cheat?" or the PBS program "Why do People Cheat?" in order to cast some doubt on the idea that there will be a time when there will be little pressure to cheat--and to cast some doubt on the idea that there is no connection between how one behaves as a student and how one will behave as a scientist, professional, or ordinary citizen. For an excellent resource on the extent to which lying can directly and indirectly cause harms to liars, those to whom lies are told, third parties who are affected by lies, and social practices and institutions we value, teachers might consult Sissela Bok's Lying: Moral Choice in Public and Private Life (New York: Random House, 1978). A very useful resource for both teachers and students is Honor in Science, published by Sigma Xi, the Scientific Research Society (North Carolina: Research Triangle Park, 1991). This clearly written 41 page publication concentrates on the importance of honesty in scientific research.

    Another ethical issue:

    There is another ethical issue this lesson raises. This has to do with a deceptive feature of the lesson itself. It is the teacher who introduces the discrepancy between data and expectation by deliberately mislabeling the resistor. The irony of a teacher using deceptive tactics in order to make a point about honesty in scientific practice is not likely to be lost on thoughtful students. They may not bring this to the attention of the teacher, as they may feel uneasy about challenging the ethics of their teacher. However, this does not mean they won't be thinking about this (and discussing it outside of class). But if the ethics of the teacher's tactic is raised, how should the teacher respond? Not only has the teacher deceived the students, he or she used this deception in order to tempt students to engage in unethical behavior themselves (viz., to falsify data). This, too, is bound to be noticed by the students. In fact, since some of them have been "caught with their hands in he cookie jar," they might be highly motivated to point their fingers back at what they take to be equally culpable behavior on the part of their teacher.

    So, there is a substantial risk that this lesson, as presently designed, will backfire. It could generate some distrust of the teacher--who, after all, has lied to the students in a way that they might perceive as manipulative. If students can say to their teacher, "See, you behave unethically, too," much of the force of the lesson may well be lost. In any case, the teacher risks losing ethical credibility with the students--a very heavy price to pay for an ethics lesson!

    Is there any alternative way of getting students to deal effectively with the ethical issues this lesson is designed to raise? One way would be for the teacher to describe this lesson to the students without asking the students to conduct the experiment themselves. This puts matters in the third person (since they will be talking about what others have done rather than themselves). Shifting the focus in this way will take some of the dramatic excitement from the lesson, but it does not change the basic ethical issues, which are inherently interesting in any case. Furthermore, students can still draw on their own experience of witnessing or engaging in cheating themselves in order to enliven their discussion of the issues this lesson raises. Not having their backs against the wall (as they would if caught in the act), students might well be in a better position to deal with the ethical issues more fairly and dispassionately.    



    Series Circuit

    NYS Required Laboratory

    Objective - To create a series circuit and to determine if the rules for a series circuit are valid:

    VT= V1 + V2

    IT = I1 =I2

    RT= R1 + R2


    1. Assemble the circuit below using a 10 ohm and 50 ohm resistor for R1and R2, respectively. Double check that the potential control is set to zero before you start assembling the circuit.


    2. Turn the dial on the power supply until the VT meter reads 10 V.

    3. Log all the meter readings in your data table.

    4. Turn the power off, remove the 10 ohm resistor, and replace it with the 5 ohm resistor. Repeat the above procedure.

    5. Turn the power off. Remove the 50 ohm resistor, and replace it with the 10 ohm resistor. Repeat the above procedure.

    6. Complete the data table for all three trials.


    VT V1 V2 IT I1 I2 R1=V1/I1 R2=V2/I2 RT=VT/IT RT=R1+R2
    5, 10                    
    5, 50                    
    10, 50                    


    1.You have two values for the resistors you used, a calculated value and the value printed on the resistor. Explain where any discrepancies between the two values may have come from.

    2. Explain in detail whether the results of this experiment validate the three equations listed in the objective. Show equations to prove your point.

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