Transcript probability - lesson 5

Probability (5)
Independent Events
3/12
2/12
1/12
3/10 x 3/5 = 9/50
Multiplied together
Independent Events
The 2 events are independent if the result of
one had no impact on the result of the other
e.g. rolling a dice and flipping a coin
Rule:
P(A B) = P(A) x P(B)
“The probability that events A and B occur is :the probability that event A occurs multiplied
by the probability event B occurs”
Example:
What students are studying at school.
Are the events ‘the student is male’ and
‘the student studies art’ independent?
Boys are less likely Male
to take art Female
than you may expect
Art
27
48
75 Artists
not Art
83
92
175 non-artists
110
Male
140
Female
250 pupils
P(art) = 75/250 = 0.3
P(male) = 110/250 = 0.44
P(male and art) = 27/250 = 0.108
For independent events: P(male
Not the same.
So not independent.
art) = P(male) x P(art)
= 0.44 x 0.3
= 0.132
Activity
Page 45 of your Statistics 1
book and try …
• Exercise
• 1, 2
C
The totals must
always add to 1
Activity
Page 48 of your Statistics 1
book and try …
• Exercise
D