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Homework Help: Different significant digits in uncertainty and data?

  1. Feb 1, 2012 #1
    Hi, I've just got a question about uncertainties that came up while doing a lab report.

    I have a set of data for currents required to cancel the deflection of an electron beam caused by the earth's magnetic field:

    0.195 A
    0.220 A
    0.250 A
    0.251 A
    0.239 A

    Because of the difficulty in measuring the straightness of the beam, my lab partner and I decided on an uncertainty of +/-0.05 A.

    Do I need to round the currents to one less decimal place because of my uncertainty, or can I keep everything as is?
  2. jcsd
  3. Feb 2, 2012 #2


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    Staff Emeritus
    Science Advisor
    Homework Helper

    Welcome to PF.

    If ±0.05 A is the uncertainty in each individual measurement, then yes, I would report the measurements to just 2 decimal places.
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