3.1  Bias and variability

3.1.1  Bias

3.1.2  Bias vs variability

3.2  Independence and non-independence

3.2.1  Independence of measurements

3.2.2  Independence of factor effects

3.2.3  Independence of sample composition.

3.3  Play!

3.3.1  Virtual two-horse races

3.3.2  More (virtual) coin tossing

3.3.3  Fair and biased coins

3.3.4  No longer independent

bias, causality, coin tossing, confounding variables, context effects, controlled experiment, day effects, effective sample size, estimate, estimate of the variability, experimenter effects, external non-independence, extreme values, factor effects, fair coin, fair estimate, Fitts' Law, independence, individual differences, interference effect, interference effects, internal non-independence, learning effects, model the bias, negative correlation, non-independence, order effects, peripheral vision, positive correlation, real world, sample composition, sample size, Simpson's paradox, snowball sample, social network data, standard deviation (s.d., σ), standard deviation of the population, standard deviation of the sample, systematic effects, unbiased, uniformity fallacy, unintentional bias, user experience, user studies, variability, variance