CallCentreVoice Topic Staffing to abandon rate v Staffing to service level

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David Bothamley on 8/4/2011 15:18:02.
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David Bothamley
Senior Manager, MI and Resourcin
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Staffing to abandon rate v Staffing to service level  [8/4/2011 15:18:02]

Excel WFM models & scheduling to meet a service goal

I have Excel models that I have used for many years. When tested and using the same inputs as I would using EWFM Aspect and Total View will produce the same results.
I have just started with a new company and the question was raised, can we forecast the abandoned rate.

The inputs are,
Call Volume, Arrival Pat, AHT, Service Level 80/20, Productivity, Absence and Leave, Scheduled Staff.

The out Puts are,
Required Staff, Over Under, Traffic Intensity, Agent Occupancy, Erlang-C Function, Immediate Answer %, Forecast service level, ASA

Two points......

1) Can some one tell me the formular I need to use forecast the abandoned rate using Excel and using some of the above data or do I require additional information.

2) Is it better the to staff to abandon rate or target service level, (i have alway staffed to SL)

Any help with be much appreciated.

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Dave Appleby
WFM & Business Telephony Manager
Healthcare Insurance

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Staffing to abandon rate v Staffing to service level  [8/4/2011 15:30:31]

David,

Nice question!

Humm.....................

Without knowing your models current formulae it's
going to be hard to know if yours can be modified plus
the fact that most Erlang models assume that there's a 'hold until
answered' it's tricky,

However, I can tell you from stuff I've seen in the past
that provided you have an average time to ABA available
to factor in it is possible to reverse PART of the calculation.

The problem is Erlang is, by it's nature, a trapdoor algorithm
so it's VERY difficult to 'unscramble the eggs' and get input data
from a required output data set. What you can do is work with the
service level and historical data to map ABA Vs forecast Vs actuals
to give an idea of..

i) The actual ABA rate at interval level

ii) Where it's happening.

iii) How it blends with your forecasts.

This should then allow you to model theoretical abandonment
(not ideal I know!) against forecast plan. Next step being
to take the 0% ABA Erlang model and apply the shortfall ABA figure.
You *should* then be able to re-model target Svc Level at a given ABA.

Hope that makes *some* sense!

I'm open t being challenged on this one, as I think
it's a really good point!

Regards

DaveA


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David Bothamley
Senior Manager, MI and Resourcin
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Staffing to abandon rate v Staffing to service level   [8/4/2011 16:03:59]

Reversing the Erlang-C not so easy, any other thoughts on staffing to a set abandoned rate or forecasting the abandoned rate.

My logic tells me that is you have the Calls offered, ASA, and Over/Under and Service Level, along with traffic intensity there must be some calculations to calculate the abandoned rate based of current staffing.

Please open to any challenge to this, Any thoughts on this welcome…

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Dave Appleby
WFM & Business Telephony Manager
Healthcare Insurance

1566 posts
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Staffing to abandon rate v Staffing to service level  [8/4/2011 16:34:58]

OK.....

To be clear..

We know

Intensity
Forecast Arrival (interval)*
Current ACTUAL staff*
Current REQUIRED staff*
Service Level
Service level variance
Staff Variance *
Current ABA rate*
Current Average time to ABA*
Curent Ans Speed SLA*
Current Svc Level SLA

So..

I concur, you must be able to model a theoretical abandon rate
based on the known ABA rate Vs Forecast and Actual staff. I've a feeling
that the % Service level is redundant within this one.

I'm not in the office and I'd like a whiteboard to play with this one
so, I'll have a play and see if I can think of a single equation
to model it. I think the ones marked with a star are core to the equation
so will have a muck around with them.

I may not get chance to hammer it into Excel!

regards

have a fun Weekend.

DaveA

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David Bothamley
Senior Manager, MI and Resourcin
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Staffing to abandon rate v Staffing to service level  [8/4/2011 17:08:52]

Comfirmed fields....

Half Hour 08:00
Interval 08:30

Monday
% Calls Offered 100.0% 1.47%
Calls Forecasted 544 8
Talk Required Officers 54.4 1.6
Agents Required 84.8 3
Agents Scheduled 114.0 4.0
Over / Under 29 1

Call Volume: 544
AHT 6.0
RE: 10
AHT Sec 360
F/c Service Level: 83.09%
Productivity: 70%
Holiday 10.0%
Absence 5.0%
Target Answer Time seconds 20

Traffic Intensity (U) 2
Agent Occupancy (RHO) 0.40
Erlang-C Function 0.1
SLVL Fomular 0.92
Agent Occupancy percent 40%
Immediate Answer percent 91%
Expected Service Level percent 92%
Average Speed Of Answer seconds 14

Theses are the exact field, any question let me know...

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Dave Appleby
WFM & Business Telephony Manager
Healthcare Insurance

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Additional  [8/4/2011 17:23:16]

Average Abandon rate currently and Average delay to abandon?

Ta

DaveA

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Pamposh Raina
Sr.Manager -Workforce management
American Express

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abandon rate  [11/4/2011 16:55:15]

caught this question while i was closing for the day. Will read it at home and get back to you

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