Database Reference
In-Depth Information
The confidence limit
of a population mean is normally given by X' +/- ZS
E
where
Z is determined by the normal distribution of the curve, considering the percentage
confidence limit required. The following Z values should be memorized:
•
68% confidence => Z = 1.64
•
95% confidence => Z = 1.96
•
99% confidence => Z = 2.58
The confidence limit defines where an occurrence X may lie in the range (X' - ZS
E
)
< X < (X' + ZS
E
), given a certain confidence. As you practice solving sampling problems,
your confidence in using the formulas will improve.
A3.5 Observation and Document Review
Review of source documents will provide useful information about the input, data
storage, and output requirements of the software system. This activity could also
provide useful information on the processing requirements of the software system. To
illustrate, get a hold of an application form at your organization, and attempt to identify
information entities (object types) represented on the form. With a little thought, you
should be able to identify some or all of the following entities:
•
Personal Information
•
Family/Kin Contact Information
•
Education History
•
Employment History
•
Professional References
•
Extra Curricular Activities
Internal documents include forms, reports and other internal publications; external
documents are mainly in the form of journals and other professional publications. These
source documents are the raw materials for gaining insights into the requirements of the
system, so you want to pay keen attention to them.
With respect to observation, it is always useful to check what you have been told
against what you observe and obtain clarification where deviations exist. Through keen
observation, the software engineer could gather useful information not obtained by other
means.
A3.6 Prototyping
In prototyping, the user gets a “trial model” of the software and is allowed to critique it.
User responses are used as feedback information to revise the system. This process
continues until a software system meeting user satisfaction is obtained.
