1. STF 1093 Statistics for Biology LU2: Basic Probability

2. Learning Objectives At the end of this learning unit, the students must be able to: Define experiment, outcome, event, probability and equally likely. Restate the formula for finding the probability of an event. Determine the outcomes and probabilities for experiments. Recognize the difference between outcomes that are equally likely and not equally likely to occur. Apply probability concepts to complete exercises.

3. 5.1 The Meaning of Probability 3 Probability is used to describe RANDOMor CHANCESof events to occur. Every day we are faced with probability statements involving the words: 1. What is the likelihood that X will occur? 2. What is the chance that Brazil will win the 2010 World Cup? 3. The upgrading of KuchingAirport will likely be completed on time. 4. There is a 50-50 possibilitythat an electricity trip will occur.

4. Let’s Recall… http://www.youtube.com/watch?v=GH0BWluXxtM&feature=related

6. For example, in an experiment of tossing a coin once, the coin landing with heads facing up is an event, since it may or may not occur.

7. The probability of an event is a measure of the likelihood of its occurrence. Probability is always expressed as a decimal and it will always fall between 0 and 1.Probability near 0 indicates that the event is very unlikely to occur. Zero (0) probability (p = 0) indicates that the event is certain not to occur. Probability near 1 suggests that the events is quite likely to occur. A probability of one (p = 1) indicates that the event is certain to occur.

9. Suppose there are N equally likely possible outcomes from an experiment.

11. 8 Example 2. A jar contains 1000 marbles, 800 are black and 200 are red. What is the probability of drawing a black marble out of the jar. Solution: Here 800 is the number of possible outcomes, f The total number of possible outcomes is 1000, N Thus the probability is and The probability of drawing a black marble is much higher than the probability of you picking a red marble because there are more black marbles in the jar.

12. Let’s Play!Probability Game http://www.youtube.com/watch?v=V6Ih87xLQfo

13. 10 5.3 Basic Probability Theorems Addition Theorems If event A and event B are mutually exclusive, then P(A or B) = P(A) + P(B) A B Because event A and event B are mutually exclusive, the total coloured region equal to the sum of the two coloured disks. For mutually exclusive events Illustrated by Venn diagram More generally if events A, B,C…..are mutually exclusive, then P(A or B or C ….) = P(A) + P(B) + P(C) + ……..

14. 11 For non-mutually exclusive events, then (A and B) – joint occurrence (A or B) The general addition rule, If A and B are two events then P(A or B) = P(A) + P(B) – P(A and B) The general notation is Probability of A  B events to occur P(A B) = P(A) + P(B) – P(A B)

15. Exercises for this week Check for weekly task in STF1093 Group in Facebook http://www.facebook.com/groups/140090106073688

17. Thank You!Any suggestions or comments??