copyright 2010, the world bank group. all rights reserved. managing coding operations section b 1

Copyright 2010, The World Bank Group. All Rights Reserved.

Managing Coding Operations

Section B

1


Creating Batches

• Homogeneity– Alike items within a batch– Helps to keep samples representative

• Batch Size– Rule-of-thumb: ½ to 1 day of work– Very small batch frequent QC, more paperwork– Very large batch delayed feedback, more rework

2


Returning Materials from the Field

• What needs to be returned from the field?

• How should these items be packed and sent, including control forms?

• Provide field staff with instructions and materials for proper returns

• Develop tracking system to verify completeness of returns at each level

• Develop receipt, unpacking and check-in procedures

3


Storage Room Operations

• Check-in should include geographic area, number of forms, and other materials by EA (map, listing sheets)

• These materials are grouped by batch, and given a batch ID that corresponds to a geocode

• Batches are shelved and tracked through processes

4


Acceptance Sampling Plan

5

The process of accepting or rejecting a lot (batch) of work by inspecting a sample selected according to a predetermined sampling plan


Acceptance Sampling Risks

• Producer’s risk (Type I error)

– Rejecting good batches

• Consumer’s risk (Type II error)

– Accepting bad batches

6


Operating Characteristic (OC) Curves

• OC Curves characterize acceptance sampling plans.

• OC Curves are graphical representations for the probability of acceptance (Pa) for every possible number of errors in a batch (p).

7


Example OC Curve

8

0

0.2

0.4

0.6

0.8

1

Pa

1 2 3 4 5 6incoming percent defective

C=6, N=200

C=12, N=400


Increasing Sample Size

9

0

0.2

0.4

0.6

0.8

1

Pa

0.02 0.04 0.06 0.08 0.1incoming fraction defective

n=400, c=2

n=240, c=2

n=80, c=2


Varying Acceptance Number

10

0

0.2

0.4

0.6

0.8

1

Pa

0.02 0.04 0.06 0.08 0.1incoming fraction defective

n=110, c=2

n=110, c=1

n=110, c=0


Acceptance Sampling Trade-Off

• Sampling Size vs. Acceptance Criteria

– Assuming a set quality level, we can make choices regarding inspection rates and acceptance criteria

– To decrease inspection rate, we must tighten acceptance criteria

– To allow more defects, we must increase sample size

11


Acceptance Sampling Inspection

• Start with 100% inspection and appropriate acceptance number for level of quality

• When a batch passes, reduce inspection on that coders work to sample inspection

• If sample inspection fails, return to 100% inspection

12


100% Dependent Acceptance Sampling

• Assign a coder’s completed batch to a verifier

• Verifier reviews all questionnaires and writes codes on separate form when they don’t agree with coder

• Supervisor compares the two and decides correct code when the coder and verifier codes differ

• An error is attributed to the coder/verifier not chosen as correct and the batch is either passed or failed

13


Sample Dependent Acceptance Sampling

• Verifier uses a random number table to choose the first questionnaire to review

• Verifier reviews all nth questionnaires afterwards until the entire batch is completed

• The supervisor then checks the sample, attributes errors and either passes or fails the batch

14


Independent Acceptance Sampling

• Assign a batch to a verifier before it is coded

• Verifier codes questionnaires on separate form

• Batch is coded by coding clerk

• Completed batch and verifier forms are checked by supervisor who attributes errors and either passes or fails the batch

15


Coding Staff Review

• Coding clerks

– Percentage increase for verification

• Supervisors as a ratio to coders

– Remember verification review work

• Assignment clerks

• Overall shift supervisors

16


Fighting Coding Boredom

• Scheduled breaks

• Rotation of duties

• Working in shifts

• Working environment

17


Staff Incentives

• Performance based

• Clear criteria for incentives

• Avoid across the board incentives

• Public recognition

• Non-monetary gifts

18


Transitioning Production Staff

• Are there subsequent activities where these staff would be useful?

• Can choose the best staff based on operational records

• Saving on recruitment could be transferred to training and other activities

19


Section B Quiz

1. What characteristics should batches have?

2. When do you plan for return of materials?

3. What is an acceptance sampling plan?

4. What does an operating characteristic curve describe?

5. Describe the use of multiple inspection methods in verification.

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copyright 2010, the world bank group. all rights reserved. managing coding operations section b 1

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