Spreadsheets and Business
Why the popularity of
spreadsheets?
• “End user Computing”
• Long delays for IS department to do
analysis and reports
• Ease-to-use, powerful software
• No need to wait for that overworked
professional programmer
• Now - anyone can write software to do
business analyses
There’s the Rub…….
• Critical business analyses
is being done by amateurs
• Think about ….
How dependent business is on
spreadsheets
and
How little validity checking is actually done!
James A. Cummings, Inc >>>
Criteria for good spreadsheet
design
• Accuracy
– testing
– Data entry controls to limit errors
• Clarity
– Easily understood by
• creator
• other users
• Flexibility
– Easily adapted
– Remains valid
Conceptual Model for
Worksheet Layout
• Input - Process - Output
• Clearly separate Input from Output
• Clearly specify Assumptions
• To be more specific …………………...
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Desirable to have separate
areas for:
Identification Area
Input Area
Assumptions / Definitions / Formulas
Work Area
Output Area
Macros
(may not have them all in every sheet.)
AMORT_TABLE.XLS >>
Tips
• Break lengthy formulas into parts
– Easily hidden later
• Use Functions Rather than Formulas
• Use Labels, Shading, Lines, Color
– anything to enhance readability
• But don’t confuse
– Form over Function
– Aesthetics over Accuracy
Cummings (2) >>>
Tips
• Clearly specify units of measure
• No Numbers In Formulas
– All placed in separate cells and referenced
• Annotate Often
• Document (i.e. Write It Down)
– Assumptions
– Formulas
No_5 template >>>>>
Tips
• Get familiar with the Auditing Toolbar
– precedents
– dependents
– Trace Error
Auditing Toolbar >>>>>
Testing
• Accuracy of Worksheet
– test with simple and predictable data
• Full range of values
• Independent Verification
– Another set of eyes
– A known test problem
• Ad Hoc Testing - Whenever using a
spreadsheet
– The ‘eyeball’ test