Oct 9-13 - Basic Probability
 
1. Chance Set-ups – PIL Ch3
 
• Chance set-up – a situation that will lead to one of a range of possible outcomes, each with some probability.
• Trial – when one of the outcomes is obtained from the chance set-up.
• Fair trial –
Unbiased outcomes
and
Independent trials
 
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all outcomes have the same probability
  
the probability does not depend on the outcomes of previous trials
• Place the examples from Q2 and Q4 (pp.33-34) on the following chart: which set-ups are fair?
Set-ups
Unbiased outcomes
Biased outcomes
Independent trials
    
Dependent trials
    
 
2. The Laws of Probability – PIL Ch 4
 
• Let Pr(X) be the probability that X is the outcome; let Ω be an outcome that is certain.
    1. (i)0 ≤ Pr(A) ≤ 1
    2. (ii)Pr(Ω) = 1 and Pr(¬Ω) = 0
    
• X and Y are mutually exclusive outcomes if they cannot both happen – Pr(X ∧ Y) = 0.
    1. (iii)If A and B are mutually exclusive then Pr(A ∨ B) = Pr(A) + Pr(B)
• X and Y are independent outcomes if the probability of X does not change depending on whether Y happened (and vice versa).
    1. (iv)If A and B are independent then Pr(A ∧ B) = Pr(A) × Pr(B)
• Place the examples from Q2-3 (pp.45-6) on the following chart: use the rules to calculate the various probabilities.
Outcomes
Mutually exclusive
Not mutually exclusive
Independent
    
Dependent