Field guide
How spreadsheets go wrong.
- Guides
- 27
- Each answers
- one question
- Tool required
- none
Guide
Why two people get different totals from the same spreadsheet.
It is almost never arithmetic. It is nearly always one of four structural problems, and each leaves a signature you can look for.
Guide
How to tell a real finding from a coincidence.
Most findings that fall apart do so for one of four reasons, and all four can be checked in minutes.
Guide
Five things to check before you trust a dashboard.
A dashboard is a set of decisions someone made and then hid. These are the five worth surfacing before you act on one.
Guide
Finding duplicates that Remove Duplicates will not find.
The built-in tool compares cells. Real duplicates disagree in every field, which is exactly why they survived.
Guide
Why Excel changes your numbers without telling you.
Four conversions happen on open, none of them warns you, and all four are irreversible once you save.
Guide
Comparing two versions of a spreadsheet without drowning in false changes.
Three things break a file comparison, and all three make it report far more changes than happened, or far fewer.
Guide
Dates in more than one format, and why it is worse than it looks.
A date column in two formats silently misplaces rows in every period comparison, and about a third of them cannot be recovered at all.
Guide
Why your CSV opens as one column, and what that means.
The most common CSV complaint has nothing to do with the file, and the second most common one is invisible until somebody searches for a customer.
Guide
Numbers stored as text, and the total that is quietly short.
The most dangerous data problem is the one whose symptom is a number that looks about right.
Guide
Joining two spreadsheets, and the match rate nobody reports.
The join usually works. What goes wrong is that nobody checks how much of it worked.
Guide
When the average describes nobody.
The mean is the right answer to a narrower question than most people are asking when they compute one.
Guide
Six ways a chart misleads without containing a false number.
Almost every misleading chart contains only true numbers. The misleading part is the encoding.
Guide
The data dictionary, and why inheriting a file without one costs a week.
The cheapest document in analytics to produce, and the one whose absence causes the most repeated work.
Guide
Analysing survey results without measuring who answered.
Sample size does not fix a systematic absence, and it is the absence that breaks most survey conclusions.
Guide
Why two dashboards give different numbers for the same thing.
Two people are usually both right about a number, and disagreeing about which number it is.
Guide
Analysing survey results in Excel when half the answers are words.
A survey export mixes ratings, tick-boxes and sentences in one grid, and each of the three needs different handling before any of them can be averaged.
Guide
Cleaning a messy spreadsheet in the order that saves the most work.
Order matters more than effort. Each repair done out of sequence has to be done again after the one it depended on.
Guide
Turning a Power BI report into a presentation without screenshotting it.
A dashboard is built for monitoring and a meeting needs an argument. The move between them starts from the data model, not from the screen.
Guide
The messy-file test: a reproducible way to check whether a data tool gets the numbers right
Most AI data tool reviews compare speed, price and charts. This one tests whether the numbers are correct.
Guide
We compute every figure twice. Here is what happens when the two answers differ.
A language model may decide what to compute. It never decides what the answer is.
Guide
Eight things that are actually wrong with your messy CSV
A CSV is not messy in general. It is usually broken in one of eight recognizable ways.
Guide
A dashboard is not a set of charts
A dashboard is not a set of charts. It is a small number of decisions, each backed by a number someone can verify.
Guide
A deck built from a spreadsheet has to survive being questioned
A data deck succeeds in the meeting after the one where it was presented, when somebody asks where a number came from.
Guide
The famous spreadsheet errors were not arithmetic errors
The famous failures were not bad maths. They were correct calculations performed on the wrong rows, ranges or types.
Guide
Julius AI alternatives, and the four questions that actually decide between them
Nearly every comparison is written by one of the products on it. This one says so, and includes the cases where the competitor is the better choice.
Guide
A close that balances is not the same as a close that is right
A close that balances can still be wrong. These checks catch the structural failures a trial balance cannot see.
Guide
The question is not whether the model is clever. It is whether it is allowed to decide the answer.
The important question is not whether the model is clever. It is whether the model is allowed to decide the answer.