Coaching practices for Building Base Rate Data

Describe almost anything you are working through and IX Coach finds the practices whose real-world fit is closest. For Building Base Rate Data, these are the strongest matches in the current practice library.

Does this sound like the set of challenges you might be facing?

• I build my estimate from my own optimistic story first and only glance at how long these things usually take at the very end as a sanity check
• When I look for examples of people who did what I’m about to do, all I find are the success stories
• One story has completely sold me on something and I’m about to act on it
• Each project wraps up and I move straight on without ever writing down what I’d guessed versus what actually happened
• I always build my whole story first

Practices that may help

1. Base-Rate Neglect: Why We Ignore the Odds
   Base-rate neglect is the tendency to underweight or ignore prior probabilities (how often things happen in general) when vivid, specific information is available. Identified by Kahneman and Tversky, it is one of the most robustly replicated biases in judgment research, and it leads to systematic overconfidence in predictions about specific cases. Correcting it requires actively looking up or estimating base rates before evaluating individual information.
2. Anchor on the base rate before adding inside-view details
   Start your forecast from the class median, then adjust — do not start from your narrative and adjust to the base rate.
   Reference Class Forecasting
3. Actively seek disconfirming cases
   When researching base rates, specifically look for cases where things went badly — failure cases are underrepresented in natural memory.
   The Outside View
4. Reference Class Forecasting
   Reference class forecasting, developed by Daniel Kahneman and Amos Tversky and formalized by Bent Flyvbjerg, improves forecast accuracy by anchoring on the statistical distribution of outcomes for similar past projects rather than on the details of the current one. The method reliably corrects the optimism bias that inflates cost, time, and benefit estimates in planning — the evidence base here is real and specific.
5. Ask the base rate before evaluating the specific case
   Before judging any individual instance, first establish how often this kind of thing happens in general.
   Base-Rate Neglect: Why We Ignore the Odds
6. Conduct post-project debriefs to contribute to the class data
   Record actual vs. forecast outcomes honestly — this builds the reference class that future forecasts depend on.
   Reference Class Forecasting
7. Lead with statistics, then interpret with narrative — not the reverse
   Use the base rate as your anchor, then adjust for your specific situation — not the other way around.
   The Availability Heuristic: Why Memorable Feels Probable
8. Always identify the denominator when evaluating risk or success
   When a number or story is striking, ask: "Out of how many total cases?"
   Base-Rate Neglect: Why We Ignore the Odds
9. Use reference class forecasting for project estimates
   Estimate how long similar projects have taken historically before estimating your specific project.
   Base-Rate Neglect: Why We Ignore the Odds
10. Anchor on base rates before adding details
    Start with how common the outcome is in the relevant population, then update — don’t start with the story.
    The Conjunction Fallacy — When "More Details" Feels More Likely

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