Use our Index of Dispersion Calculator to quickly determine if your count data is overdispersed, underdispersed, or fits a Poisson distribution. Input your dataset and analyze the variance-to-mean ratio for crucial statistical insights.
Formula:
The Index of Dispersion (ID), also known as the Variance-to-Mean Ratio (VMR), is calculated as:
ID = s2 / μ
Where:
- s2 (Variance): A measure of how far a set of numbers are spread out from their average value.
- μ (Mean): The average of the numbers in your dataset.
- If ID < 1: The data is underdispersed.
- If ID ≈ 1: The data follows a Poisson distribution.
- If ID > 1: The data is overdispersed.