Transcript Chapter 19 Designing Accurate Data

Chapter 19
Designing Accurate
Data-Entry Procedures
Systems Analysis and Design
Kendall and Kendall
Fifth Edition
Major Topics
Data entry
Effective coding
Types of codes
Guidelines for coding
Validation methods
Check digits
Ecommerce accuracy
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Quality Data-Entry Objectives
The quality of data input determines
the quality of information output
Accurate data entry is achieved through
four broad objectives:
Effective coding
Effective data capture
Efficient data capture and entry
Assuring quality through validation
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Codes and Coding
Coding helps efficiency because
Data that are coded require less time to
enter
Coding helps to reduce the number of
items entered
Coding can help in sorting of data during
the data transformation process
Coded data can save valuable
memory/storage space
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Purpose of Coding
Besides providing accuracy and
efficiency, coding does the following:
Keeping track of something
Classifying information
Concealing information
Revealing information
Requesting appropriate action
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Types of Codes
Types of codes are
Simple sequence code
Alphabetic derivation codes
Classification codes
Block sequence codes
Cipher codes
Significant digit subsets
Mnemonic codes
Function codes
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Simple Sequence Code
Identify a person, place, or thing in
order to keep track of it
A number that is assigned to something
if it needs to be numbered
It has no relation to the data itself
Order Number
Product
5676
Rocking Chair
5677
Dining Room Table
5678
Love Seat
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Alphabetic Derivation Codes
A commonly used approach in
identifying an account number
The code becomes the account number
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Alphabetic Derivation Codes
First five digits come from the first five digits of
the subscriber's zip code
Next three are the first three consonants in the
subscriber's name
Next four numbers are the street address
Last three make up the code for the magazine
Code
68506KND7533TVG
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Format of Code
99999XXX9999XXX
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Advantages of Alphabetic
Derivation Codes
Advantages
Can have zip code in front for sorting
A requirement for bulk mailing
A magazine subscription may be used
weekly for mailing
Can verify a person calling about their
account
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Disadvantages of Alphabetic
Derivation Codes
Disadvantages
Names like ROE - become RXX
Street addresses like 12 OAK STREET code contains 1200
Changing name or address results in the
key field being changed
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Classification Information
Coding affords the ability to distinguish
between classes of items
Classes must be mutually exclusive
Classification Codes
Used to distinguish one group of data
with special characteristics from another
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Classification Information
Consist of either a single letter or a
number
A shorthand way of describing a person,
place, thing, or happening
Classification codes are listed in
manuals or posted so that users can
locate them easily
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Classification Codes
Use a single letter for a code
Code
I
M
T
C
D
S
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Tax Deductible Item
Interest Payments
Medical Payments
Taxes
Contributions
Dues
Supplies
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Classification Codes Problems
Code
I
M
T
C
D
S
B
P
N
X
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Tax Deductible Item
Interest Payments
Medical Payments
Taxes
Contributions
Dues
Supplies
Subscriptions
Computer
Insurance
Miscellaneous
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Block Sequence Codes
An extension of the sequence code
Advantages
That the data are grouped according to
common characteristics
The simplicity of assigning the next
available number (within the block) to the
next item needing identification
Can do inquiries on code beginnings
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Block Sequence Code
Code
100
101
102
200
201
202
300
301
400
401
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Name of Software Package
Netscape
Internet Explorer
Lynx
Access
Paradox
Oracle
Word
WordPerfect
Astound
Micrograf Designer
Type
Browser
Database
Word Processing
Presentation
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Cipher Codes
Codes may be used to conceal or
disguise information
Cipher Codes
Direct substitution of one letter for
another, one number for another, or one
letter for a number
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Cipher Codes
Code Meaning
B
1
Style Code
L
2
E
3 GOLDEN’S
A
4 202-395-40
C
5 BIMC
H
6
M
7 Size 12
I
8 $25.00
N
9
D
0
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Revealing Information
Sometimes it is desirable to reveal
information through a code
Make the data entry more meaningful
Allows persons to view the code and
understand what it means
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Significant Digit Subsets
Used to describe a product via its
membership in many subgroups
The advantage of using a significantdigit subset code is the ability to locate
items that belong to a certain group or
class
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Significant Digit Subsets
Can do inquiries on portions of the code
Look for matching red items, other size 10
items, other maternity, or similar dresses
Code
Merchandise Described
2023954010 Red maternity dress, style 395, size 10
202
395
40
10
Department (maternity)
Product (dress style 395)
Color (red)
Size (size=10)
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Mnemonic Codes
A mnemonic (pronounced nî-môn'-ïk) is
a memory aid
Any code that helps data-entry person
remember how to enter the data or
End user remember how to use the
information
Uses a combination of letters and
symbols
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Function Codes
Codes are often necessary for
instructing either the computer or the
person about actions to take
Function Codes
Spelling out precisely what activities are
to be accomplished is replaced by the
use of a short numerical or alphabetic
code
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Guidelines for Coding
Guidelines for coding
Keep codes concise
Keep codes stable
Make codes that are unique
Allow codes to be sortable
Avoid confusing codes
Keep codes uniform
Allow for modification of codes
Make codes meaningful
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Keep Codes Concise
Overly long codes mean more
keystrokes and consequently more
errors
Long codes also mean the information
in the files will require more memory
If codes must be long, they should be
broken up into subcodes
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Keep Codes Stable
Stability means that the identification
code for a customer should not change
each time new data are received
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Make Codes That are Unique
Assure that codes are unique
Make a note of all codes used in the
system
Do not assign the same code number or
name to the same items
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Allow Codes to be Sortable
The codes must be sortable
Problem date: MMMDDYY
First three symbols are the month as a
three-letter abbreviation
Second two are the date as a number
Last two digits are the year
Numerical codes are much easier to sort
than alpha-numeric data
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Avoid Confusing Codes
Avoid using coding characters that look
or sound alike
O (the letter oh) and 0 (the number zero)
Letter I and the number 1
Letter Z and the number 2
Codes such as B1C and 280Z are confusing
Canadian Postal Code
The code format is X9X 9X9
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Keep Codes Uniform
Follow readily perceived forms most of
the time
Avoid using the codes MMDDYY in one
application
YYDDMM in a second
MMDDCCYY in a third; CC - century
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Allow for Modification of Codes
The system will evolve over time
The coding system should be able to
encompass change
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Make Codes Meaningful
Effective codes contain information
They should make sense to people
using them
Meaningful codes are easier to
understand, work with, and recall
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Using Codes
Codes are used
In validation programs to ensure that only
valid codes have been entered
In report and inquiry programs to display
code meanings
In GUI programs to create drop-down lists
This helps to ensure accurate data, since
the user sees the code and it’s meaning
and can only select a code from the list
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Effective Data Capture
In order to assure the quality of data
entered into the system, it is important
to capture data effectively
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Guidelines for Effective Data
Capture
Guidelines for effective and efficient
data capture
Deciding what to capture
Letting the computer do the rest
Avoiding bottlenecks and extra steps
Starting with a good form
Choosing a data-entry method
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Validation Overview
To assure data quality, errors should be
detected during input, prior to
processing and storage
Two possible ways to validate inputs
are:
Validation of input transactions
Validation of input data
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Data-Entry Methods
Data-entry methods include
Keyboards
Optical character recognition
Magnetic ink character recognition
Mark-sense forms
Bar codes
Intelligent terminals
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Problems With Input Data
Three main problems that can occur
with input transactions are
Submitting the wrong data to the system
Submitting of data by an unauthorized
person
Asking the system to perform an
unacceptable function
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Validation Methods
Validation methods include
Test for missing data
Test for correct field length
Test for class or composition
Test for range or reasonableness
Test for invalid values
Cross-reference checks
Test for comparison with stored data
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Check Digits
Check digits are used to validate a
numeric field by performing a
calculation on a part of the number and
comparing the result with a digit stored
within the number
Check digits help to detect
Single digit miskey
Transposition errors
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Check Digits
There are several check digit methods:
Modulus
Modulus
Modulus
Modulus
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10,
10,
11,
11,
“2-1-2” method
“3-1-3” method
arithmetic method
geometric method
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Check Digit General Method
Start with the numeric code
Choose the weighting method and
modulus number
Multiply the digit by the chosen weight
Sum the new numbers
Divide by the modulus number
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Check Digit General Method
Remaining Steps
Compute the check digit by taking the
modulus number and subtracting the
remainder
Subtract again if greater than 10
Add check digit to the end of the
number
Use this new code for data entry and let
the computer validate the code
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Modulus 11 Arithmetic Method
Number 2 9 6
4 5
Weights 6 5 4
3 2
Product 12 45 24 12 10
Original number
29645
Sum of products = 103
Divide 103/11 = 9 remainder 4
Checkdigit = 11- 4 = 7
Final number
296457
9R4
11 103
-99
4
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11
- 4
7
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Using Codes
Codes may be included in drop-down
lists when using a GUI interface
This helps to ensure that the data
entered are accurate, since the user
sees both the code and it’s meaning
and can only select a code from the list
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Ecommerce Accuracy
Ecommerce environments have
increased accuracy of data because
Customers generally enter data themselves
Data entered by customers are stored for
later use
Data entered at the point of sale are used
throughout the order fulfillment process
Information is used as feedback to
customers
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