percentages

[azteca]

hi, first time user
I am working in a project and i need to find out the formula for the
following example:
first month 28% positive results second month 26% positive results 3rd month
29%
so comparing month to months there was a -2% between 1st and 2nd month and
an +3% increase from 2nd month to 3rd month.
how can I display the results in a cell so it will show -% or +% depending
on the percentage per month?

 

[Nigel]

Is it a case of subtracting the later value from the former 26% - 28% = -2%

So if the first value is in A1 and the second in B1 then in C1 enter =B1-A1

However this may not be what you want? The difference is actually 2
percentage points, not necessarily 2%. To compute the true percentage
variance you must know the underlying data from which the individual
variances are derived; unless the denominator for the original percentages
are the same, in that case the points movement is equal to the true
percentage.

 

[azteca]

thanks for replying
let me see if I can describe it better, we take a number of calls, say 253,
then we rate them in groups of great, good, fair, and poor then we divide
each group by the total number (253) thus we get the percentage for each
group. the percentage may vary for the same group in month one and month two,
let's say "great" calls were up 60% in the 1st month and 57% 2nd month or
viseversa 57% 1st mo 60% 2nd mo
I need to display in a cell the diffenrece wheater +3% or -3% just by
changing the number of calls for that group.
The cells with the total % of calls have the formula already.

 

[SteveM]

thanks for replying
let me see if I can describe it better, we take a number of calls, say 253,
then we rate them in groups of great, good, fair, and poor then we divide
each group by the total number (253) thus we get the percentage for each
group. the percentage may vary for the same group in month one and month two,
let's say "great" calls were up 60% in the 1st month and 57% 2nd month or
viseversa 57% 1st mo 60% 2nd mo
I need to display in a cell the diffenrece wheater +3% or -3% just by
changing the number of calls for that group.
The cells with the total % of calls have the formula already.

What Nigel is saying above is that stating percent change for both the
total number of calls and each call category may mislead the reader.
For example, 3% of 252 rounds to 8. Meanwhile, 60% of 253 is 152.
And 3% of that rounds to 5. So if you say there was a 3% change in
the category do you mean 8 calls or 5 calls in absolute terms. You
have to be very clear on what the basis of the percentage is.

Versteh?

SteveM