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Conclusions drawn from scientific investigations are influenced by both controllable and uncontrollable errors. The purpose of this lab was to quantify fluctuations in measurements and consider these when interpreting data outcomes. Answer the questions below in your lab records to conclude today’s lab.

  1. State your general claim from lab 01. In lab 01 your group made a claim which addressed the research question “What affects the period of a pendulum?” Restate that claim here. Be sure to indicate the conditions for which the claim holds. This includes the values held constant (CVs) as well as the range of values tested for the IV.
  2. Cite the evidence that supports your claim.
    • Consider a hypothetical exercise.Two students wish to reduce the random error in measuring the period in their pendulum experiment. Which student do you agree with? Explain your reasoning.
    • Consider a second hypothetical exercise.Two students measure the mass of a ring three times using the same balance and get slightly different values: 17.46 g, 17.42 g, 17.44 g. They wish to minimize any experimental error. What might they do? Choose the best option below and explain your reasoning for this selection.
      1. This variation is due to random error. The students should take more data. Random errors can be reduced by averaging over a large number of observations.
      2. This variation is due to systematic error. The students should take more data. Systematic errors can be reduced by averaging over a large number of observations.
      3. There is no way to minimize experimental error.

    The data collected during lab 02 may be used to modify your claim, if warranted. The following questions serve as a guide for evaluating all evidence that supports your original or revised claim.

    • i.How confident are you in the values obtained for each measurement of the period? Be sure to comment on the sizeof the ranges of uncertainty (error bars) for these measurements.
    • ii.Consider whether values on graph are equivalent.It is common convention to draw error bars as ±σ (one standard deviation). If the ranges of uncertainty for two values overlap, then a claim can be made that the values may bethe same. One can’t know for sure that the values are the same! If there is no overlap, however, then a claim can be made that the values are different.
    • iii.Consider the best fit line or curve on each graph. How confident are you that your line or curve accurately describes the relationship between your IV and DV?

    Your graphs from lab 01 now include error bars. In light of the discussion about overlapping error bars, does your group’s general claim made during lab 01 still hold? If it is no longer true, state a revised claim here.

    Student 1:I believe that we should measure the time for the pendulum to swing for 6 complete cycles and then divide by 6 to get the time for one single period. This will reduce the overall random error associated with starting and stopping the stopwatch.

    Student 2: I disagree that this is the best approach. The pendulum will slow down enough by the 6thswing that the measured time will no longer be accurate.

    Be sure you have explained your reasoning for the selection above.

    Check your lab records for completeness using the rubric below:

    Excellent (12)

    Limited (6-11)

    Missing (0-5)

    Responses to the Final Wrap Up Questions

    Thoroughly addresses questions and provides evidence, if requested, for:

    a.State claim and conditions for claim from lab 01 (2)

    b.Cite evidence that supports claim (6)

    1. Evaluate data and observed patterns

    i. Discuss confidence in measurements

    ii. Use error bars to determine whether values on graph are equivalent. Modify claim(s), if warranted.

    iii. Discuss confidence in trend line

    c.Hypothetical exercise (2)

    d.Second hypothetical exercise (2)

    Some of the question responses are missing, are not complete, or are incorrect.

    A significant number of question responses are missing or are incorrect.

    Checkpoint 3! Be ready to discuss with your lab instructor how the inclusion of uncertainty impacts claims and/or one’s confidence in those claims. Also, be ready to discuss your responses to the two hypothetical exercises.

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