Variance and Standard Deviation for Conditional and Marginal Distributions

Free SOA Exam P (Probability) lesson in Multivariate Random Variables. 15 min read, ~2,269 words.

Eve's law:, within + between. Variances add, SDs do NOT: always work with variances, take square root at the end. If all conditional means equal: between-group term vanishes. If all conditional variances zero: within-group term vanishes. Between-group component can dominate: segment heterogeneity may exceed inherent randomness.

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