Input Controls

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Chapter 11

• Input Controls

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Data Input Methods
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Source Document Design Auditors Concerns

• 1) It reduces the likelihood of data recording
  errors.
• 2) It increases the speed with which data can be
  
• recorded.
• 3) It controls the work flow.
• 4) It facilitates data entry into a computer
  system.
• 5) For patter recognition devices, it increases
  the
• speed and accuracy with which data can be
  read.
• 6) It facilitates subsequent reference checking.

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Design Guidelines

• Preprint wherever possible
• Provide titles, headings, notes, and instructions
• Use techniques for emphasis to highlight
  differences
• Arrange fields for ease of use
• Use the caption above fill-in area approach
• Provide multiple choice answers
• Use tick marks to identify field-size errors
• Combine instructions with questions
• Conform to organizational standards

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Data-Entry Screen Organization

• Screens should be designed so they are
  uncluttered and symmetrically balanced.
• Layout of elements on screen must mirror the way
  in which data is obtained during the data-capture
  task.
• Design should be used repeatedly across
  applications.

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Data Entry Screen Design

• Tabbing and skipping
• Color
• Response time
• Display rate (fast)
• Prompting and help facilities

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Prompting Facility
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Help Facility
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Data Coding Errors

• Addition (extra character for zip)
• Truncation (omit character)
• Transcription (wrong character o or 0)
• Transposition (78 or 87)
• Double transposition (87942 as 84972)

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Factors Affecting Coding Errors

• Length of the code (hard to remember if too long)
• Alphabetic/numeric mix (lower error rate)
• Choice of characters( avoid B I O S V Z)
• Mixing uppercase/lowercase fonts (not good)
• Predictability of character sequence (THE vs. ZXQ)

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Types of Coding Systems

• Serial Codes
• assign consecutive numbers to an entity,
  irrespective of the attributes of the entity
• Block Sequence Codes
• assign blocks of numbers to particular categories
  of an entity (CUST starting with 201 or 202 have
  discount of 2)
• Hierarchical Codes
• require selection of the set of attributes of the
  entity to be coded and their ordering by
  importance(C65 division , 423 depart , and 3956
  type expense)
• Association Codes
• attributes are selected and unique codes are
  assigned to each value SHM32 means shirt for male
  size 32

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Association Code example

• Code assigned to a shirt
• SHM32DRCOT
• where SH shirt
• M male
• 32 32 centimeters neck size
• DR dress shirt
• COTcotton fabric

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Check Digits

• Check Digit-- a redundant digit added to a
  code that enables the accuracy of other
  characters in the code to be checked.
• E.g., 2148 , 214815, drop tens, then
• 21485 that prevents simple transposition error
  

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Efficiency of Check Digit Methods

• 1967 study found the frequency of errors to be as
  follows
• Transcription 86
• Single transposition 8
• Double transposition 6
• and random
• See page 437 for more complex examples

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Efficiency of Different Moduli for Check Digits
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Batch Controls

• Types of Batches
• Physical batches
• Logical batches

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Means of Batch Control

• Batch cover sheet contains
• a unique batch number
• control totals for the batch
• data common to the various transactions
• date when the batch was prepared
• information on errors detected in the batch
• space for signatures of batch handlers

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Types of Data Input Validation Checks

• Field Checks
• Record Checks
• Batch Checks
• File Checks
• (Reporting data input errors)

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Menu-Driven Languages
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Question -Answer Dialogs
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Forms-based Languages
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Types of Instruction Input Validation Checks

• Lexical Validation
• Syntactic Validation
• Semantic Validation (similar to syntactic)

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Accounting Audit Trail

• Instruction input audit trail might record
• the identity of the originator of the instruction
• the time and date when the instruction was
  entered
• the identifier of the physical device used to
  enter the instruction
• the type of instruction entered and its arguments
• the results produced in light of the instruction

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Operations Audit Trail

• Operations audit trail data that might be kept
• time to key in a source document or instruction
  at a terminal
• number of read errors made by a scanner
• number of keying errors identified
• frequency with which an instruction is used
• time taken to invoke an instruction w/ light pen
  versus a mouse