This document discusses common spreadsheet errors: 1) Copying and pasting incorrect data from multiple spreadsheets without thorough checking due to time constraints. 2) Updating column names and formulas in a pivot table incorrectly, resulting in wrong formulas. 3) Developing different parts of a complex model independently without proper documentation, leading to incorrect combined results. 3) Developing a model without understanding all relevant variables from different groups, missing important data.

1. Spreadsheet disasters
Nipun Mathur
April 4, 2010

2. Error #1
Scenario
My boss asked me to perform a quick analysis for his
meeting in 1 hour
Problem
Copy pasted data from different spreadsheets to get
job done on time. Paster incorrect data, from miss-
matching dates. Performed back of the envelope
check but, no time to run extensive checks.
Error type
Mechanical error

3. Error #2
Scenario
Performing analysis on data with many degrees of
freedom requiring pivot table analysis.
Problem
Want to arrange analysis columns differently from pivot
table’s alphabetically ordered columns. Updated column
names, applied formula to the first column, and dragged
formula to all other cells. Formulae now incorrect for
columns.
Error type
Logic error

4. Error #3
Scenario
Working on a complex model with a team of people over
multiple weeks.
Problem
Each person developing different parts of the model. The
assumptions made by different people are different and
there is not enough documentation. When all parts are
put together the final model produces incorrect results.
Error type
Documentation and planning error

5. Error #4
Scenario
Working on a accounting analysis consulting
project, with unfamiliar data. Developed model
without speaking with all groups involved.
Problem
Missed some variables that the model results
depend on.
Error type
Data omission error

6. Error #5
Scenario
Experienced analyst developing a routine model
at the end of the day.
Problem
Misses data and doesn’t perform sanity check
because this is a routine task for him.
Error type
Overconfidence