## Summary of Formulae - Conditional Probability, Independent Events etc This is only true if A and B are independent. You can never assume A and B are independent. You must either know it or prove it. This is always true for two events A and B. The left hand side P(A divides B) is the probability that A will happen given that B has happened, often written as A given B or A conditional on B. If A and B are independent then so  This is always true.

The above equations are very useful when working with Venn diagrams.

Correlation Coefficients and Regression Lines where If the equation of a regression line of on is given by then and The unbiased estimate of the standard deviation of a random variable found from a list of n numbers is given by where If the expectation value – often called the mean, average, and written or – of a random variable is given by and then and  and for all distributions, but if the distribution is continuous we may use and  and for a continuous distribution etc. for a continuous distribution. 