Statistics II: Tips

Abdullah Al Mahmud

Chapter 01: Introduction to Probability

  • \(^6C_3 = \frac{6!}{3!(6-3)!}\); use calculator to save time

Random Variable

  • Random variable: a variable whose outcomes are associated with probability (having no sure-fire outcome)
  • Marginal vs joint events (see here)
  • Marginals probabilities (P(X)) are obtained by adding joint probabilities (P(x,y))
  • If conditional probability is \(P(X|Y), P(X|0) = P(X|y=0)\)
  • \(P(X|0)\) means if y = 0, what is probability of x?

Expetation

  • \(V(X) < SD(X)\) if \(0 \lt V(X) \lt 1\) or \(V(X)\) is greater

Binomial Distribution

    • To find \(P(X\ge 3); n=15\), use \(1-P(X \lt3)\) or calculator (if you don’t have computer with you)