Transcript Chapter 4 Topics – Sampling – Hard data – Workflow analysis – Archival documents Sampling • A process of systematically selecting representative elements of a population • A System.

Chapter 4
Topics
– Sampling
– Hard data
– Workflow analysis
– Archival documents
Sampling
• A process of systematically selecting
representative elements of a
population
• A System analyst has to make a
decision on 2 key issues:
– Which of the key documents and Web
sites should be sampled
– Which people should be interviewed or
sent questionnaires
Need for Sampling
• The reasons systems analysts do sampling are
– Reduction of costs
• More time & cost involves to ask all employees, reading all web
pages
• Redundant data
– Speeding up the data-gathering process
• Little burden to gather sampled data rather than all data
– Improving effectiveness
• Ask detail questions to few employees which requires little time and
the analyst can follow up on missing and incomplete data
– Reduction of data-gathering bias
• i.e. Biased interview by the executive who like to see the project
successful
Sampling Design Steps
• To design a good sample, a systems analyst
needs to follow four steps:
– Determining the data to be collected or described
• Identify attributes, variable, associated data item
• Data gathering methods like interview, questionnaire,
observation etc.
– Determining the population to be sampled
• Duration of analysis (i.e. 2 month, 1 year)
• Determine whether interview should take place on one level
or all level of organization or outside of the organization
– Choosing the type of sample
– Deciding on the sample size
Four Types of Sampling
• Convenience samples
– System analyst post a notice asking everyone
interested in new sales performance report to come
to a meeting at 1 PM on 12th December
– Easiest to arrange but most unreliable
• Purposive samples
– Analyst chooses group of knowledgeable individuals
who are interested in the field
– Moderately reliable
Four Types of Sampling (contd.)
• Simple Random Sampling
–
–
–
–
Based on a numbered list of the population
Each person or document has an equal chance of being selected
Choose every k-th element
Not always practical
• Complex Random Sampling
– Has three forms
• Systematic sampling:
– select every k-th element like simple random sampling
• Stratified sampling:
– sub group the population (i.e. executive level, line level) & then
sample
• Cluster sampling:
– select a group of document or people to study
– There are many “sonali” bank around the country. Investigate 1
or 2 of them
Sample Size
• Sample size depends on the cost as well
time required by the system analyst
• Sample size under ideal condition is
determined by:
– Sampling data on attributes
– Sampling data on variables
– Sampling qualitative data
Steps to Determine Sample Size for Attribute Data
– Determine the attribute to sample
– Locate the database or reports where the
attribute is found
– Examine the attribute and estimate p, the
proportion of the population having the
attribute
– Make the subjective decision regarding the
acceptable interval estimate, i
– Choose the confidence level and look up the
confidence coefficient (z value) in a table
– Calculate σp, the standard
error of the
i
p=
proportion asσfollows:
z
Steps to Determine Sample Size for Attribute Data
(Contd.)
– Determine the necessary sample size, n,
using the following formula:
p(1-p)
n=
+1
2
σp
Confidence Level Table
99%
98%
97%
96%
95%
90%
80%
50%
2.58
2.33
2.17
2.05
1.96
1.65
1.28
.67
Hard Data
• In addition to sampling, investigation of hard
data is another effective method for systems
analysts to gather information
• Hard data can be obtained by
– Analyzing quantitative documents such as records
used for decision making
– Performance reports
– Records
– Data capture forms
– E-commerce and other transactions
Workflow Analysis
• Workflow analysis may reveal signs of larger problems,
such as
• Data or information doesn’t flow as intended
– Too many or too few people, wrong people receiving it
• Bottlenecks in the processing of forms
• Access to online forms is cumbersome
– e.i. Web forms must be printed and then sent rather
than electronic submission
• Unnecessary duplication of work occurs because
employees are unaware that information is already in
existence on another form that they don’t know
• Employees lack understanding about the interrelatedness
of information flow
– e.i. they don’t know that their output works as input to
another person
Archival Documents
• A systems analyst may obtain some
valuable information by abstracting
data from archival documents
• Generally, archival documents are
historical data, and they are prepared
and kept by someone else for specific
purposes