## 6706Re: [webanalytics] Re: basic math question - percentages

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• Jun 1, 2006
Maureen,

not a math genius either, but if you converted 10 people out of 100 in
April and 12 out of 100 in May, you converted 20% more people in May
than in April, and you converted 10% in April and 12% in May, and your
conversion rate went up by 20% (like the number of peoble you
converted), so only your first example seems to be literally correct.

-Oliver

On 01/06/06, HAKIMALY@... <HAKIMALY@...> wrote:
> Technically both are correct, however it is more common the refer to the difference between two %s as "percentage points difference". In banking, the difference is referred to as "basis points", where 1 basis point= 1/100 of 1%. So, 1%=100bp, and 0.2% = 20bp.
>
> Hakim
>
>
> Andrew Edwards <aedwards@...> wrote:
>
> >I'm no math genius but I am pretty sure the *increase* between 1% and
> >1.2% is 20%. It might also be called (uncharitably) an additional 0.2%
> >overall on total percentage of conversions, but then you're confusing
> >the word "additional" with the notion of "increase by percentage".
> >
> >--Andrew Edwards
> >
> > Ted Callier wrote:
> >
> >>On Wed, 31 May 2006 19:38:39 -0000
> >>"matpflum" <matpflum@...> wrote:
> >>
> >>
> >>
> >>>I have always struggled with the logic behind this seemingly simple
> >>>question. Doesn't it make more sense to say that if the conversion
> >>>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
> >>>
> >>>
> >>
> >>If you want to show the difference by doing a substraction, this is
> >>called "percentage point", .2 percentage points(not .2% !) in your
> >>example.
> >>
> >>If you use percentages, you can apply them to percentages w/o problems
> >>as long as both measure the same thing, conversion in your example.
> >>
> >>So conversion increased by 20%, or .2 percentage points, from 1% in
> >>March to 1.2% in April.
> >>
> >>And as you have no reason to believe me, see youself what Wikipedia has to say:
> >>http://en.wikipedia.org/wiki/Percentage and http://en.wikipedia.org/wiki/Percentage_point
> >>
> >>
> >>
> >>
> >>
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> >>
> >>
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--

Viele Grüße,
Oliver
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