1. Normal distribution
Each binomial distribution is defined by n, the number of trials and p, the
probability of success in any one trial.
Each Poisson distribution is defined by its mean.
In the same way, each Normal distribution is identified by two defining
characteristics or parameters: its mean and standard deviation.
The Normal distribution has three distinguishing features:
• It is unimodal, in other words there is a single peak.
• It is symmetrical, one side is the mirror image of the other.
• It is asymptotic, that is, it tails off very gradually on each side
but the line representing the distribution never quite meets the
horizontal axis.