Probability
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N5 LS
Expected Frequency
Probability Tree
Exam Type Questions
31-Jul-17
Created by Mr. Lafferty
1
Starter Questions
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N5 LS
31-Jul-17
Created by Mr.Lafferty Maths Dept
Probability
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N5 LS
Learning Intention
1. We are learning to
calculate probability
frequency.
31-Jul-17
Success Criteria
1. Be able to calculate
probability frequency.
Created by Mr Lafferty Maths Dept
Probability
N5 LS
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To work out a probability
number of outcomes
P(A) =
Total number of possible outcomes
Probability is ALWAYS in the range 0 to 1
31-Jul-17
Created by Mr Lafferty Maths Dept
Probability
N5 LS
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Expected Frequency
EF(A) = P(A) x ( Total number of events)
31-Jul-17
Created by Mr Lafferty Maths Dept
Expected Frequency
Ball goes back
into the bag.
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N5 LS
1
2
3
4
5
What is the chance of picking the number 3 ?
P(3) =
1
5
= 0.2
If I repeat this 40 times how many times can
I expect to pick out 3 ?
EF(3) = 0.2 x 40 = 8
31-Jul-17
Created by Mr Lafferty Maths Dept
Expected Frequency
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N5 LS
In Kirkintilloch last year the chance of catching
the flu was 0.15. There are 19 700 people in town.
How many people are expect to catch the flu ?
EF(flu) = 0.15 x 19700 = 2995 people
31-Jul-17
Created by Mr Lafferty Maths Dept
Expected Frequency
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N5 LS
Now Try
TJ N5 Lifeskills
Ex 1 Q1 to Q6
Ch26 (page 252)
31-Jul-17
Created by Mr. Lafferty Maths Dept.
Starter Questions
N5 LS
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1.
Calculate the area of the following shapes.
5 cm
3 cm
2.5 cm
2.
3 cm
Round to nearest 100
(a) 47856
(b) 90
(c) 249.5
Q3. Explain why 15% of £360 = £54
4 cm
Probability Tree
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N5 LS
Learning Intention
Success Criteria
1. We are learning about
Probability Trees.
31-Jul-17
1. Understand Probability Tree.
2. Calculate the probability of
events happening using a
Probability Tree .
Created by Mr Lafferty Maths Dept
P(E1) = 0.2
Probability Tree
P(E2 )= 0.3
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N5 LS
Overall Probability
E2
E1
P(E1) then P(E2)
0.3
0.2
0.2 x 0.3 = 0.06
0.7
NOT E2
0.8
NOT E1
0.2 x 0.7 = 0.14
E2
P(NOTE1) then P(E2)
0.3
0.8 x 0.3 = 0.24
0.7
NOT E2
31-Jul-17
P(E1) then P(NOTE2)
Created by Mr Lafferty Maths Dept
P(NOTE1) then P(NOTE2)
0.8 x 0.7 = 0.56
P(R) – probability RAIN
P(R) = 0.6
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P(D)= 0.4
It’s Raining
P(D) – probability DRY
In November it rained on 18 days out of 30.
(i)
Create a probability tree.
(ii)
Calculate the probability that it will rain on
any two consecutive days.
31-Jul-17
Created by Mr Lafferty Maths Dept
P(R) = 0.6
What
P(3R)=the
0.6x
chance
0.6x0.6on 3
What
P(3R)=the
0.4x
chance
0.4x0.4on 3
consecutive
= 0.216
days of rain ?
consecutive
= 0.064dry days
It’s Raining
P(D )= 0.4
N5 LS
Overall Probability
R
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R
P(R) then P(R)
0.6
0.6
0.6 x 0.6 = 0.36
0.4
D
R
0.4
0.6
D
0.4
D
31-Jul-17
Created by Mr Lafferty Maths Dept
P(R) then P(D)
0.6 x 0.4 = 0.24
P(D) then P(R)
0.8 x 0.3 = 0.24
P(D) then P(D)
0.4 x 0.4 = 0.16
Have you updated your
Learning Log ?
Probability Tree
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N5 LS
Now Try
TJ N5 Lifeskills
Ex 1 Q7 ......
Ch26 (page 253)
31-Jul-17
Created by Mr. Lafferty Maths Dept.