Probability Distributions and Sampling Statistics Essentials
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Quantitative Variables
1. Discrete: values of x have "gaps" between them (ex: test scores)
2. Continuous: no gaps between x values
Random Variable X
Assigns a number to outcomes of an experiment
Probability Distribution of a Discrete X
A table, graph, or forumla that shows the values of X and P(X) where:
Expected Value of Discrete X
1. The probability distribution of x represents a population (μ,σ^2,σ)
2. Mean of X = expected value of X
(1) Discrete in General
Variance of Discrete X
Standard Deviation of Discrete X
Ex:
x | 1 | 2 | 4 |
|---|---|---|---|
| P(X) | .7 | .2 | .1 |
(2) Binomial X
- Need n, P and q
- x = # of successes in n
- P(X) use binomial tables (if n < 5) or="" the="">
- mean --> μ = nP variance --> σ^2 = nPq standard deviation --> σ = √nPq
- NOTE: Formula gives
, known as a polar coordinate.
is considered positive when measured counterclockwise and negative when measured clockwise.