Statistics Formula's 2025

Basic Probability Rules

1. Possible values for probabilities range from 0 to 1

2. The sum of all the probabilities for all possible outcomes is equal to 1

3. Addition rule - the probability that one or both events occur

4. Multiplication rule - the probability that both events occur together

5. Conditional probability - the probability of an event happening given that another event has already happend

Addition rule - the probability that one or both events occur

• Mutually exclusive events: P(A or B) = P(A) + P(B)

• Not mutually exclusive events: P(A or B) = P(A) + P(B) - P(A and B)

Mutuplication Rule - the probability that both events occur together

• Independent events: P(A and B) = P(A) * P(B)

• Dependent Events: P(A and B) = P(A) * P(B|A)

Conditional Probability - the probability of an event happening given that another event has already happened

P(A|B) = P(A and B) / P(B)

Bayes Theorem

Covariance formula

Correlation Formula’s

Formula 1:

Formula 2:

Skewness formula + interpretation

If Skewness > 0, it is a positive skew or right skew; tail is longer on the right side

If Skewness < 0, it is a negative skew or left skew; tail is longer on the left side

Hypergeometric Formula Probability

Use when calculating groups:

• Committee of 40 people

• 15 Females, 25 Males

• Calculate committee of 5 females and 5 males