Use the current data that you have for that three month period to come up
with a value that is kind of a visitor to staff ratio.
Lets say you know that with 5 staff and 40 visitors you have the 20% busy
time.
With 5 staff and 60 visitors it goes up to 30%
with 5 staff and 100 visitors it goes up to 50%
Now I cheated with the numbers to make them come up even, but it turns out
that if you reduce those numbers by lowest common denominator, you get
1 staff, 8 visitors = 20%
1 staff, 12 visitors = 30%
1 staff, 20 visitors = 50%
20% / 8 = 2.5%
30% / 12 = 2.5%
and, oddly enough,
50% / 20 = 2.5%
Your percentages will no doubt vary some, but once you get it down to those
kinds of numbers, just average the percentages (sum them all, divide by total
count of them used to get the sum). That will tell you how much time each
visitor 'costs' you in terms of a staff member's time.
Then you can set up some simple what-if tests in Excel. You could set up a
cell with the percentage of time that one visitor costs (2.5%), another cell
to put in the number of visitors you estimate will come in on a given day and
have a 3rd cell multiply the two to tell you how much of 1 staff member's
time it will take to deal with them. Lets say you think you'll have 100
visitors:
2.5% 100 visitors
2.5 * 100 = 250%
Since you know there is no such thing as 250% of 1 person's time, what that
actually tells you is that you need 2 1/2 staff members working at full speed
to keep up with the 100 visitors. Hard to hire half a person these days
(although it seems easy enough to hire one person and only get half-a-day's
work out of them <g>), so you would want at least 3 people on hand for a day
you expected 100 visitors, and you'd probably want to expect to hear
complaints from the staff about being overloaded, because the workload is
probably not going to be evenly distributed.
In Excel terms, for the first what-if, you could set it up like this:
put .025 in A1 (an unchanging constant value, 2.5% = .025 )
put the estimated number of visitors into B1 (change as you desire)
in C1 put this equation: =A1 * B1
You could even put this into D1 to get number of whole bodies you need:
=ROUNDUP(C1,0)
You can work the formula backwards, so to speak, to say "if I have this many
staff members, how many visitors can I serve?"
4 staff members = 400% time available
400% / 2.5% = 160 visitors
Again, in Excel terms:
put the percentage, .025, into A2
Put the number of staff you will have on hand (4) into B2,
in C2 put this formula: =B2/A2
again, this may not come out as a whole number, so you may want to put this
formula into D2:
=ROUNDDOWN(C2,0)
which will tell you the absolute maximum number of visitors that a staff of
whatever number you put into B2 can handle in one day.
Hope this helps you some.
