Slide 1 The Philosophical Commitments and Disputes which inform Qualitative Research
Slide Slide 1 Fundamentals of Probability. Slide Slide 2 A chance experiment is any activity or...
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Transcript of Slide Slide 1 Fundamentals of Probability. Slide Slide 2 A chance experiment is any activity or...
SlideSlide 1
Fundamentals of Probability
SlideSlide 2
A chance experiment is any activity or situation in which there is uncertainty about which of two or more possible outcomes will result.Suppose two six-sided dice are rolled
and they both land on sixes.
Or a coin is flipped and it lands on heads.
Or record the color of the next 20 cars to pass an intersection.
Chance Experiment
SlideSlide 3
Event
any collection of results or outcomes of a procedure
Simple Event
an outcome or an event that cannot be further broken down into simpler components
Sample Space
for a procedure consists of all possible simple events; that is, the sample space consists of all outcomes that cannot be broken down any
further
SlideSlide 4
Consider a chance experiment to investigate whether men or women are more likely to choose
a hybrid engine over a traditional internal combustion engine when purchasing a Honda Civic at a particular dealership. The type of
vehicle purchased (hybrid or traditional) will be determined and the customer’s gender will be
recorded.
List all possible outcomes.
This is an example of a sample space.
Sample Space
Sample space = {MH, FH, MT, FT}
SlideSlide 5
Four students (Adam (A), Bettina (B), Carlos (C), and Debra(D)) submitted correct solutions to a math contest that had two prizes. The contest rules specify that if more than two correct responses are submitted, the winners will be selected at random from those submitting correct responses.
What is the sample space for selecting the two winners from the four correct responses?
Sample space = {AB, AC, AD, BC, BD, CD}
Because the winners are selected at random, the six
possible outcomes are equally likely.
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Notation for Probabilities
P - denotes a probability.
A, B, and C - denote specific events.
P (A) - denotes the probability of event A occurring.
SlideSlide 7
Probability Limits
The probability of an event that is certain to occur is 1.
The probability of an impossible event is 0.
For any event A, the probability of A is between 0 and 1 inclusive. That is, 0 P(A) 1.
SlideSlide 8
Possible Values for Probabilities
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Basic Rules for Computing Probability
Rule 1: Relative Frequency Approximation of Probability
Conduct (or observe) a procedure, and count the number of times event A actually occurs. Based on these actual results, P(A) is estimated as follows:
P(A) = number of times A occurred
number of times trial was repeated
SlideSlide 10
Suppose that you perform a chance experiment that consists of flipping a cap from a 20-ounce bottle of soda and noting whether the cap lands with the top up or down.
Do you think that the event U, the cap landing top up, and event D, the cap
landing top down, are equally likely? Why or Why not?
SlideSlide 11
Basic Rules for Computing Probability - cont
Rule 2: Classical Approach to Probability (Requires Equally Likely Outcomes)
Assume that a given procedure has n different simple events and that each of those simple events has an equal chance of occurring. If event A can occur in s of these n ways, then
P(A) = number of ways A can occur
number of different simple events
sn =
SlideSlide 12
Basic Rules for Computing Probability - cont
Rule 3: Subjective Probabilities
P(A), the probability of event A, is estimated
by using knowledge of the relevant
circumstances.
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SlideSlide 15Copyright © 2007 Pearson Education, Inc Publishing as Pearson Addison-Wesley.
Law of Large Numbers
As a procedure is repeated again and again, the relative frequency probability (from Rule 1) of an event tends to approach the actual probability.
SlideSlide 16Copyright © 2007 Pearson Education, Inc Publishing as Pearson Addison-Wesley.
COMPLEMENT OF AN EVENT
The complement of event A, denoted by
A, consists of all outcomes in which the
event A does not occur.
SlideSlide 17
Rounding Off Probabilities
When expressing the value of a probability, either give the exact fraction or decimal or round off final decimal results to three significant digits. (Suggestion: When the probability is not a simple fraction such as 2/3 or 5/9, express it as a decimal so that the number can be better understood.)
SlideSlide 18
Odds in Probability
The actual odds against event A occurring are the ratio P(A)/P(A), usually expressed in the form of a:b (or “a to b”), where a and b are integers having no common factors.
The actual odds in favor of event A occurring are the reciprocal of the actual odds against the event. If the odds against A are a:b, then the odds in favor of A are b:a.
The payoff odds against event A represent the ratio of the net profit (if you win) to the amount bet.
payoff odds against event A = (net profit) : (amount bet)