PROBABILITY - Text version of PowerPoint slides (minus the graphics!)
Slides 3,4,12,18,21 containing questions to be answered.
Slide 3
RULES OF ADDITION
If events are exclusive:
Prob (A or B) = P(A u B)
= P(A) + P(B)
P( 1 or 6 ) = P (K or Q) =
If events are not exclusive:
P( A u B) = P(A) + P(B) - P(A n B)
Question 3.1: P(Heart or Queen) =
Question 3.2: P(Spade or Picture) =
Slide 4
A picture or listing outcomes helps
Investigate throwing two dice and
adding the totals:
How many possible outcomes are
there?
6 . . . . . .
5 . . . . . .
4 . . . . . .
3 . . . . . .
2 . . . . . .
1 . . . . . .
1 2 3 4 5 6
Find the probabilities of throwing:
Question 4.1: • a double
Question 4.2: • a total of 10
Question 4.3: • a double or a total of 10
Question 4.4: • at least one 6
Slide 12
Find the percentage or probability give information about the customers and underlying trends:
conditional probabilities look for a pattern:
age versus gender
e.g. P(30+/ F) and P(30+/M)
or P(F/<30) and P(M/<30)
Age Male Female totals
< 30 100 75 175
30+ 50 25 75
totals 150 100 250
Question: 12.1 work out probabilities of age or gender profile P(30+); P(F)
Question: 12.2 work out probabilities P(30+/ F) and P(30+/M)
Question: 12.3 work out probabilities of P(F/<30) and P(M/<30)
Slide 18
Analyse the following data using different probabilities.
What is the relationship between age, dress and buying
behaviour?
A probability case study based on actual data in USA
· 12 Up - market fashion stores selling women clothing.
· These attract many window shoppers and tourists.
· It would be useful if staff could identify serious buyers.
· The
Market Research thinks that buying pattern is affected by age and dress of
the shoppers.
Question: Work out the probabilities (percentages) of:
<40 well-dressed buyers
40+ well-dressed buyers
<40 casual buyers
40+ casual buyers
<40 well-dressed non-buyers
40+ well-dressed non-buyers
<40 casual non-buyers
40+ casual non-buyers
Percentages should add up to 100%.
Slide 21
The following information comes from the same store, but for male buyers.
Question: Analyse the data using a tree diagram and calculating probabilities.
Who should the shop assistant target?
Male buyers
· form 1/3rd of customers
· 6 out of 10 made a purchase
· of those who made a purchase 2 out of 10 wore suits
· of those who didn't make a purchase 9 out of 10 were not in a suit
Hint: probabilities should add up to 0.333 (i.e. 1/3rd of customers)
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