Mental model

Simple Averaging of Forecasts

A powerful method for improving prediction accuracy by taking the simple average of multiple forecasts, which cancels out individual errors and often outperforms a typical single forecast.

Discover

Three colleagues estimate the same project timeline: 8 weeks, 12 weeks, and 20 weeks. What estimate should you use for planning?

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Discover why simple math often beats expert judgment.

Understand

Understand

For example, if your team predicts quarterly sales will be $100K, $120K, and $140K, the average of $120K is likely closer to the actual outcome than any individual prediction. Try this: Ask at least three people for their independent forecasts, then calculate the mean of their numbers.

Full explanation

Full explanation

The mechanism relies on error cancellation—each forecaster brings unique knowledge, assumptions, and biases, so their errors tend to be uncorrelated and offset when combined.

Consider a product launch scenario: your marketing specialist predicts 5,000 units sold in the first month, your sales lead expects 8,000 units, and your finance analyst projects 6,500 units. The simple average of 6,500 units may be more accurate than any single guess because it incorporates diverse perspectives about customer behavior, market conditions, and historical data. Similarly, when planning a wedding budget, if three venue quotes are $8,000, $12,000, and $15,000, the average of $11,667 gives you a balanced expectation rather than relying on one potentially biased estimate.

The power of averaging increases with the diversity of your forecasters. In business settings, combining forecasts from sales, marketing, operations, and finance departments typically outperforms any single department's prediction. This happens because each team sees different pieces of the puzzle and makes different kinds of mistakes—some teams consistently underestimate, others overestimate, but these biases cancel in the average. Even better, this method requires no special expertise or complex calculations, making it accessible to anyone who can do basic arithmetic.

Research

Research

Simple averaging of forecasts is one of the most robust findings in prediction research, demonstrating that combined forecasts often improve accuracy over individual forecasts.

  • Armstrong (2001): Meta-analyses show that combining forecasts from different methods often reduces errors compared to using single methods, and simple averages are frequently competitive with or better than more complex weighting schemes [1].

  • Clemen (1989): Review of forecast combination research confirms that the "forecast combination principle"—that combined forecasts are generally more accurate than their components—holds across diverse domains from economics to weather prediction [2].

Limitations

Limitations

Simple averaging has important boundaries. It fails when forecasters share the same systematic biases—for example, if everyone anchors on the same misleading information, averaging will preserve rather than cancel that error. The method also struggles when there's a single expert with truly superior knowledge; averaging that expert with novices may dilute their insight. Additionally, social influence can also undermine effectiveness if forecasters see each other's predictions before making their own, reducing independence and causing errors to cluster rather than cancel.

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Check your understanding

Your team gives three project estimates: 4 months, 6 months, and 10 months. You calculate the average as 6.67 months. Why is this average likely more accurate than picking 6 months (the middle value)?

Show the guide's explanation

Answer: Averaging uses information from all three forecasts, allowing high and low errors to cancel

Simple averaging incorporates all available information rather than discarding extreme values. When forecasters make independent errors, some will be too high and others too low—averaging preserves the signal while canceling the noise. The 10-month estimate may capture risks the 6-month forecaster missed, while the 4-month estimate might reflect efficiencies the others overlooked.

A marketing team predicts holiday sales of 50,000 units, while engineering predicts 80,000 units based on production capacity. If you average these to get 65,000 units, what principle explains why this often works?

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Answer: Different perspectives bring different errors that cancel when combined

Marketing might focus on customer demand patterns while engineering considers supply constraints—each sees part of the picture. Their errors tend to be uncorrelated because they're based on different information and assumptions. When you average, the optimistic bias in one area cancels the pessimistic bias in another, leaving a more balanced estimate.

When would simple averaging of forecasts likely FAIL to improve accuracy?

Show the guide's explanation

Answer: When all forecasters base their estimates on the same flawed report

Averaging relies on forecasters making independent errors that can cancel each other out. If everyone anchors on the same incorrect information, their errors become correlated—everyone will be biased in the same direction, and averaging simply reproduces that shared error. Independence and diversity of information sources are essential for averaging to work.

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