What is the difference between a normal and a Poisson distribution?
This table summarises the most important differences between normal distributions and Poisson distributions:
Characteristic | Normal | Poisson |
---|---|---|
Continuous or discrete | Continuous | Discrete |
Parameter | Mean (µ) and standard deviation (σ) | Lambda (λ) |
Shape | Bell-shaped | Depends on λ |
Symmetry | Symmetrical | Asymmetrical (right-skewed). As λ increases, the asymmetry decreases. |
Range | −∞ to ∞ | 0 to ∞ |
When the mean of a Poisson distribution is large (>10), it can be approximated by a normal distribution.