PROBABILITY
CONDITIONAL PROBABILITY
Random variable A variable defined on a sample space. Fx: The value of a card. Interpretation: A variable that takes different values with different probabilities. (Some) Characteristics of a random variable X: Mean value E(X). Variation V(X) = E((X-E(x))^2). Graphical representation by histogram. Cumulative mass function/distribution function of a random variable: F(x) = P(X ≤ x)
BINOMIAL DISTRIBUTION
POISSON DISTRIBUTION
CONTINOUS DISTRIBUTIONS
NORMAL DISTRIBUTION
LOG-NORMAL DISTRIBUTION
Fractile/QQ-plots How can we access information about the distribution of a sample? By comparing fractiles – the QQ-plot in SPSS. The proposed distribution is good, if the fractiles follow a linear pattern. Notice: The variability of the points decreases when the sample size increases. The variation of the points around the line is largest in the ends. Hence, pay more attention to the points in the middle of the plot. Detrended QQ-plots The points should be spread evenly above/below the horizontal line. There should be no pattern.
Examples of QQ-plots Normal distributionSkew distribution Uniform distribution QQ-plot Detrended QQ-plot