Common mistakes that make reports misleading

In this lesson

Recognise the recurring errors that make a technically correct report misleading
Check a report for these before sharing it

A report can be built correctly, in the sense that every number is calculated as intended, and still mislead its reader. The errors that cause this are less about arithmetic and more about scope, comparison, and disclosure, and the same handful recur across most misleading reports.

Wrong population, right calculation

The most common mistake is including or excluding the wrong people without realising it. A utilisation report that quietly includes people on parental leave as zero-utilised will understate the team’s actual performance; one that excludes recent joiners because their record is incomplete will overstate it. Neither error is visible in the number itself, only in knowing who was counted.

Mismatched comparison periods

Comparing this month’s utilisation to last quarter’s average, without saying so, makes a stable figure look like a trend or a real trend look stable. This happens most often when a report is updated over time and the comparison baseline is never refreshed to match - the current figure moves forward each month, but the baseline it is measured against silently stays fixed to when the report was first built.

Hidden assumptions

A report that shows a single number for “utilisation” without stating how utilisation is defined - does it count planned work or only confirmed billable work, does part-time capacity count pro-rata - invites the reader to apply their own assumption, which may not match yours. Two readers can draw opposite conclusions from the same chart if each is silently assuming a different definition.

State who is included and excluded from the population, in one line, on the report itself.
Confirm the comparison period matches what the current figure is measured over - same length, most recent equivalent.
State how the headline term is defined, if it is not obvious - what counts as utilised, confirmed, or available.
Ask a colleague unfamiliar with the report to state back what it shows, before it goes to its actual audience.

None of these checks take long, and each one closes a gap where a technically correct report would otherwise lead its reader to the wrong conclusion.

Key takeaways

A correct calculation on the wrong population is still a misleading report
Mismatched date ranges between current and comparison figures quietly distort a trend
A report that hides its own assumptions invites the wrong conclusion