Calculating Percentage of Errors
Date: 03/21/2002 at 20:57:28 From: Rod McComas Subject: Calculating % of errors What is a good formula for calculating % of errors when you have items to be picked off a shelf every day? You pick one item a day and check it against the order. You wish to assign a percentage to the error in wrong items and/or number of items. At the end of the month you wish to calculate the combined percentage correct, percentage of incorrect items, and percentage of incorrect quantities. I looked at (100%/number of items picked) * number incorrect (100/50) * 50 = 100% and doing an average at the end of the month. %/number of audited pickings. Interested in any better ideas! Rod McComas
Date: 03/22/2002 at 13:02:21 From: Doctor Douglas Subject: Re: Calculating % of errors Hi, Rod, Thanks for submitting your question to the Math Forum. Here's the way I would do it. First, on a given day find the number of items N on the audited order.See how many line items are filled incorrectly, and call this number W. Then percentage errors in filling items would be P = (100) x (W/N) This number will be only the percentage "wrong" on that day. Of course the numbers N and W will change from day to day. You can choose two numbers Y and Z for distinguishing between wrong items and wrong quantities: Y and Z, since any error in filling will either be a problem in what kind of item (Y), or the quantity (Z). Obviously W >= Y and W >= Z, although it's not necessarily true that W = Y + Z, since a wrong line item could be *simultaneously* an error in type and quantity. We keep track of all the numbers (i.e. number of line items is N1,N2,...,N30 in a month of thirty days). Then, at the end of the month, you add up all the numbers N, W, Y, and Z from all days in that month, and you can compute the same ratios: (100) x [W1+W2+...+W30] / [N1+N2+...+N30] percentage "wrong" (100) x [Y1+Y2+...+Y30] / [N1+N2+...+N30] percentage "wrong kind" (100) x [Z1+Z2+...+Z30] / [N1+N2+...+N30] percentage "wrong qty" - Doctor Douglas, The Math Forum http://mathforum.org/dr.math/
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