Mean Percentage Error Calculator

MPE Formula:

\[ MPE = \frac{1}{n} \times \sum \left( \frac{Actual - Forecast}{Actual} \right) \times 100 \]

Mean Percentage Error (%):

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1. What is Mean Percentage Error (MPE)?

Definition: MPE measures the average percentage difference between actual and forecasted values.

Purpose: It helps assess the accuracy of forecasting models by showing the average percentage error.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ MPE = \frac{1}{n} \times \sum \left( \frac{Actual - Forecast}{Actual} \right) \times 100 \]

Where:

\( MPE \) — Mean Percentage Error (%)
\( Actual \) — Observed actual values (unitless)
\( Forecast \) — Predicted forecast values (unitless)
\( n \) — Number of observations

Explanation: The formula calculates the average percentage difference between actual and forecasted values.

3. Importance of MPE Calculation

Details: MPE helps evaluate forecasting model accuracy. Positive values indicate under-forecasting, negative values indicate over-forecasting.

4. Using the Calculator

Tips: Enter comma-separated lists of actual and forecast values. Both lists must have the same number of values and actual values cannot be zero.

5. Frequently Asked Questions (FAQ)

Q1: What does a positive MPE mean?
A: Positive MPE indicates the forecast is systematically lower than actual values (under-forecasting).

Q2: What does a negative MPE mean?
A: Negative MPE indicates the forecast is systematically higher than actual values (over-forecasting).

Q3: What's a good MPE value?
A: Closer to zero is better. The acceptable range depends on your specific application and industry standards.

Q4: Why can't actual values be zero?
A: The formula divides by actual values, so zero would cause division by zero errors.

Q5: How does MPE differ from MAPE?
A: MPE can be negative (showing direction of error) while MAPE (Mean Absolute Percentage Error) is always positive.