QA Calibration Variance
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 This topic has 4 replies, 4 voices, and was last updated 3 days, 2 hours ago by Strayer.

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October 7, 2020 at 9:31 am #250349
How do we compute the variance per question and not the overall score?
Facilitator Evaluator1
Score Score
Item1 10 0
Item2 0 10
Total 10 10They seem calibrated as they have the same total but looking closely, but items 1 and 2 are both answered differently.
Thank you
0October 7, 2020 at 11:36 am #250350
Robert ButlerParticipant@rbutler Include @rbutler in your post and this person will
be notified via email.It’s just the sums of the squares of the deviation from the mean divided by the total count minus 1.
So, for a single item the average is (10 + 0)/2 = 5
The deviations from the mean are
10 – 5 = 5
05 = 5
The squares of those deviations are
5^2 = 25
(5)^2 = 25
there are two observations so 2 – 1 = 1
Therefore the variance per item is (25 + 25)/1 = 50 and the standard deviation is the square root of 50 = 7.07
If this were a real situation, my first reaction would be: why bother with any calculations – better to find out why two different individuals are coming up with ratings that are the exact opposite of one another. As presented, if the two raters are the system, then there is no calibration whatsoever.
0October 17, 2020 at 1:00 pm #250501
Chris SeiderParticipant@cseider Include @cseider in your post and this person will
be notified via email.October 17, 2020 at 3:30 pm #250505
Robert ButlerParticipant@rbutler Include @rbutler in your post and this person will
be notified via email.Things are fine on my end @cseider – hope all is well with you too. As for the homework – it’s pretty quiet around these parts and I was feeling generous… :)
0October 18, 2020 at 9:39 pm #250524
StrayerParticipant@Straydog Include @Straydog in your post and this person will
be notified via email.This is off topic but I insist that we distinguish between QA and QC. The main reason is that we can easily overlook QA when it’s conflated with QC. Quality Control is testing, inspection, and analysis to verify that a product conforms to specifications, plus the related actions to handle nonconformance. Quality Assurance is the systematic monitoring and evaluation of the various aspects of a project, service, or facility to ensure that standards of quality are being met.
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