OCR MEI S1 2009 June — Question 4

Exam BoardOCR MEI
ModuleS1 (Statistics 1)
Year2009
SessionJune
TopicDiscrete Probability Distributions
TypeCalculate Var(X) from table

4 The table shows the probability distribution of the random variable \(X\).
\(r\)10203040
\(\mathrm { P } ( X = r )\)0.20.30.30.2
  1. Explain why \(\mathrm { E } ( X ) = 25\).
  2. Calculate \(\operatorname { Var } ( X )\).