when to use virtual hold technology in call centre operations

OR54 Conference, Edinburgh, Sept 2012.

When to use Virtual Hold Technology in Call Centre Operations

Dave Worthington, Chris KirkbrideDepartment of Management Science,Lancaster University, [email protected]@lancaster.ac.uk

(Thanks to Zubin Sethuraman, MSc student, Lancaster University).


Outline

Energy provider call centre context Previous work on balking queues Do our models fit? Model predictions Implications for call centre management.

2


US Energy Provider:Daily call volumes to call centre (Winter)

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Days

Dai

ly C

alls

s

ACQUISITIONS CARE PAYG


Hourly: call volumes & ASAs (mins)

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Time of day

CARE ACQUISITIONS PAYG

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Hourly: ASAs (mins) & abandonment %s

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The problem posed

Virtual hold technology (VHT) gives callers opportunity to be called back without losing their place in the queue (accept /stay in queue/ balk)

When should they use VHT? Should they use it differently for

different queues?


7

Reminder


Time-dependent queues with balking Balking can be used to represent balking and reneging We investigate M(n(t))/G/S and assume geometric balking, i.e.

Snbt

Sntt Snn )(

)()( 1

Impact of balking on Arrival Rates

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no. in system

arriva

l rat

e

Strong

Medium

Weak

Time-dependent arrival rate (t)

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0 6 12 18 24 30 36 42 48

Time

arri

val ra

te


Results: Easy-to-use approximation

Queue length behaviour of M(n(t))/G/S can be approximated (well) by a Normal distribution with:

)1ln(

1(t))variance(n

)1ln(

))(ln(5.0E(n(t))

b

b

St

S


Self Validation Property

Approximation works well when Prob (n<S) is small, which we can check using standard Normal tables, e.g. Prob(n<S) < 0.05 if mean is >=1.645 SDs above S, i.e.:

)1ln(645.1))(ln( i.e.

)1ln(645.1))(( i.e.

bSt

bStnE


Results: Easy-to-use approximation

Anticipated Queueing Time (AQT):

Sb

St

)1ln(

))(ln(5.0

(t))AQTE(

)(S served customers of Percentage t

Abandonment behaviour:


‘Sub-optimal’ behaviour is frequent

100%100%% S_util

20%20%% balked

1.253.41AQT0.95

0.642.25E(AQT)

11.844.0E(Q)Perf’mancemeasures

0.9820.995B

2020S

2525System Parameters

BASystem

100%100%% S_util

20%20%% balked

1.253.41AQT0.95

0.642.25E(AQT)

11.844.0E(Q)Perf’mancemeasures

0.9820.995B

2020S

2525System Parameters

BASystem

Impatience is a virtue!


CARE: non-balking % V queue length/server

Queue length/server

Non-b

alk

ing %

100%

6.0

50%

0.0

b*(off) =0.8205

b*(on) = 0.8578


ACQU’: non-balking % V queue length/server

Queue length/server

Non-b

alk

ing %

100%

2.5

50%

0.0

b*(off) =0.6773

b*(on) = 0.7361


PAYG: non-balking % V queue length/server

Queue length/server

Non-b

alk

ing %

100%

6.0

20%

0.0

b*(off) =0.7807

b*(on) = 0.8091


Performance prediction tool:

Sb

St

)1ln(

))(ln(5.0

(t))AQTE(

… based on:

ASA


ASA analysis: CARE calls

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Predicted

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Predicted (-1)



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Predicted

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Pred (+VHT)



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Predicted

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ASA analysis: PAYG calls

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Predicted

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Pred (+VHT-1)


ASA analysis: ACQUISITION calls

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Hour of day

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Predicted (S)

Predicted (S+1)

Predicted (S-1)

Pred (+VHT)

Pred (+VHT+1)

Pred (+VHT-1)


ASA analysis: What if …….. 1?

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ACQ

CARE (S)

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PAYG (S-1)



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PAYG (S+1)



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CARE (S)

CARE (&VHT)

PAYG (S)

PAYG (&VHT)


Management implications

VHT is not necessary for Acquisition calls For other call types VHT reduces

abandonments and therefore increases ASAs!

So do current results suggest that VHT is a bad idea? Depends how many customers accept VHT Maybe depends on call centre agent

allocation software And …………………?

when to use virtual hold technology in call centre operations

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