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6715Re: [webanalytics] Re: basic math question - percentages

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  • Minni Masi
    Jun 1, 2006
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      Hi all,

      IMHO

      If the conversion rate went from 1% to 1.2% which means that the conversion
      rate went up by 20%, it's ok to state that. It just depends, as long as the
      opther party understands what you are saying

      LOL

      MM



      On 6/1/06, Peter Michael Sopp <peter.sopp@...> wrote:
      >
      > I'm just a poor sociologist not a mathematician. Nevertheless I'm hoping
      > I could clarify the points already mentioned by others.
      > The main point is to understand that the result of a substraction is a
      > difference and not a percentage.
      > The difference is April - March, so 1% - 1.2% = 0.2%-points. The result
      > of a substraction is always a absolute number and never a percentage!
      > To calculate the percentage growth or percentage increase you need a base:
      > (April-March)/March = simple growth rate. Now you can multiply it by 100
      > and you get 20% (= growth rate in percent: The difference of the
      > percentages is related to the percentage of March).
      > Let's give an interesting example:
      > a1t1 = absolute number of visitors in March
      > a2t1 = absolute number of buyers in March
      > pt1 = percentage buyers March (buyers related to visitors:
      > (a2t1/a1t1)*100)
      > a1t2 = absolute number of visitors in April
      > a2t2 = absolute number of buyers in April
      > pt2 = percentage buyers April (buyers related to visitors:
      > (a2t1/a1t1)*100)
      > Now the following could happens: The number of visitors as well as the
      > number of buyers decrease. Nevertheless the growth rate is positive
      > because relativly more visitors has converted to buyers in April as in
      > March.
      > For example: In March you have a simple conversion rate of
      > (10/1000)*100 = 1% and in April (6/500)*100=1.2%.
      > The conclusion is - well that's up to you!
      > Hope this was helpful
      > Peter
      >
      > matpflum schrieb:
      > > I have always struggled with the logic behind this seemingly simple 0
      > > rate was 1% in March and is 1.2% in April, that the rate increased
      > > by .2% and not 20%? So it's a simple subtraction. I'm not a
      > > mathematician, but I think that it is wrong to compute a percentage
      > > of a percentage because the percentages were calculated off of
      > > different bases. Are there any mathematicians who can explain which
      > > way is correct? Thanks.
      > > Maureen
      > >
      > >
      > >
      >
      >
      >
      >
      >
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