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Apr 21, 2023Apr 21, 2023
Quartiles from a Frequency Table
Quartiles from a Cumulative Frequency Table
StatisticsStatisticsw
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Estimating Quartiles from C.F Graphs
Standard Deviation
Scatter Graphs
Standard Deviation from a sample
Probability
Relative Frequency & Probability
S5 Int2
Apr 21, 2023Apr 21, 2023
Starter QuestionsStarter Questions
1. Calculate the mean, median, mode and range
f or the weekly wages £ 200, £ 100, £ 800
£ 160, £ 100, £ 380, £ 120 and £ 180.
2. Make a Cumulative f requency table f or
a batch of eggs graded in sizes 1 - 7.
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StatisticsStatistics
Learning IntentionLearning Intention Success CriteriaSuccess Criteria
1.1. Know the term quartiles.Know the term quartiles.1. To explain how to calculate quartiles from frequency tables.
2.2. Calculate quartiles given a Calculate quartiles given a frequency table.frequency table.
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Quartiles from Frequency TablesS5 Int2
Quartiles from Frequency Tables
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StatisticsStatisticsw
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Reminder !
S5 Int2
Range : The difference between highest and Lowest values. It is a measure of spread.
Median : The middle value of a set of data.When they are two middle values the median is half way between them.
Mode : The value that occurs the most in a set of data. Can be more than one value.
Quartiles : The median splits into lists of equal length.The medians of these two lists are called quartiles.
Quartiles from Frequency Tables
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StatisticsStatisticsw
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S5 Int2
To find the quartiles of an ordered list you consider its length. You need to find three numbers which break the list into four smaller list of equal length.
Example 1 :For a list of 24 numbers, 24 ÷ 6 = 4 R0
6 number 6 number 6 number 6 numberQ1 Q2 Q3
The quartiles fall in the gaps between Q1 : the 6th and 7th numbersQ2 : the 12th and 13th numbersQ3 : the 18th and 19th numbers.
Quartiles from Frequency Tables
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S5 Int2
Example 2 :For a list of 25 numbers, 25 ÷ 4 = 6 R1
6 number 6 number 6 number 6 numberQ1
Q2
Q31 No.
The quartiles fall in the gaps between Q1 : the 6th and 7th
Q2 : the 13th Q3 : the 19th and 20th numbers.
Quartiles from Frequency Tables
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S5 Int2
Example 3 :For a list of 26 numbers, 26 ÷ 4 = 6 R2
6 number 6 number 6 number 6 number
Q1
Q2
Q3
1 No.
The quartiles fall in the gaps between Q1 : the 7th numberQ2 : the 13th and 14th numberQ3 : the 20th number.
1 No.
Quartiles from Frequency Tables
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S5 Int2
Example 4 :For a list of 27 numbers, 27 ÷ 4 = 6 R3
6 number 6 number 6 number 6 number
Q1 Q2 Q3
1 No.
The quartiles fall in the gaps between Q1 : the 7th numberQ2 : the 14th numberQ3 : the 21th number.
1 No.1 No.
Quartiles from Frequency Tables
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Example 4 :For a ordered list of 34. Describe the quartiles.
8 number 8 number 8 number 8 number
Q1
Q2
Q3
1 No.
The quartiles fall in the gaps between Q1 : the 9th numberQ2 : the 17th and 18th numberQ3 : the 26th number.
1 No.
34 ÷ 4 = 8 R2
Apr 21, 2023Apr 21, 2023
Now try Exercise 1Start at 1b
Ch11 (page 162)
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StatisticsStatisticsS5 Int2 Quartiles from Frequency Tables
Apr 21, 2023Apr 21, 2023
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1. Multiply out the brackets and simplif y
4(y+ 3) - 3(8- x)
2. Find the gradient and the y - intercept
f or the line with equation 2y = - 4x + 10
3. Find the quartiles f or the ordered 6 numbers
10, 12, 14, 18, 22, 30,32
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StatisticsStatisticsQuartiles from Cumulative Frequency Table
1. To explain how to calculate quartiles from Cumulative Frequency Table.
1.1. Find the quartile values Find the quartile values from Cumulative Frequency from Cumulative Frequency Table.Table.
S5 Int2
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TimeTime Freq.Freq.
(f)(f)
Example 1 :
The frequency table shows the length of phone calls ( in minutes) made from an office in one day.
2
5
4
8
3
1
2
3
4
5
2
10
22
18
5
Cum. Freq.Cum. Freq.
S5 Int2
StatisticsStatisticsQuartiles from Cumulative Frequency Table
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StatisticsStatisticsQuartiles from Cumulative Frequency TableS5 Int2
We use a combination of quartiles from a frequency table and the Cumulative Frequency Column.
For a list of 22 numbers, 22 ÷ 4 = 5 R2
5 number 5 number 5 number 5 number
Q1
Q2
Q3
1 No.
The quartiles fall in the gaps between Q1 : the 6th number Q1 : 3 minutes
1 No.
Q2 : the 11th and 12th number Q2 : 4 minutesQ3 : the 17th number. Q3 : 4 minutes
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No. Of No. Of SectionsSections
Freq.Freq.
(f)(f)
Example 2 :
A selection of schools were asked how many 5th year sections they have.Opposite is a table of the results.
Calculate the quartiles for the results.
3
8
8
9
5
4
5
6
7
8
3
16
33
25
8
Cum. Freq.Cum. Freq.
S5 Int2
StatisticsStatisticsQuartiles from Cumulative Frequency Table
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StatisticsStatisticsQuartiles from Cumulative Frequency TableS5 Int2
We use a combination of quartiles from a frequency table and the Cumulative Frequency Column.
The quartiles fall in the gaps between Q1 : the 8th and 9th numbers Q1 : 5.5Q2 : the 17th number Q2 : 7
Q3 : the 25th ad 26th numbers. Q3 : 7.5
Example 2 :For a list of 33 numbers, 33 ÷ 4 = 8 R1
8 number 8 number 8 number 8 numberQ1
Q2
Q31 No.
Apr 21, 2023Apr 21, 2023
Now try Exercise 2Ch11 (page 163)
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StatisticsStatisticsQuartiles from Cumulative Frequency Table
Apr 21, 2023Apr 21, 2023
Starter QuestionsStarter Questionsw
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1. Find the area of the triangle.
2. Write down the two conditions
f or using the cosine rule.
3. Find the length of AC.
S5 Int2
A
B
C
8cm53o
70o
4cm
2cm3cm29o
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1. To show how to estimate quartiles from cumulative frequency graphs.
1.1. Know the terms quartiles.Know the terms quartiles.
2.2. Estimate quartiles from Estimate quartiles from cumulative frequency cumulative frequency graphs.graphs.
S5 Int2
Quartiles fromQuartiles fromCumulative FrequencyCumulative Frequency
GraphsGraphs
Quartiles fromQuartiles fromCumulative FrequencyCumulative Frequency
GraphsGraphs
Number of sockets
Cumulative
Frequency
10 2
20 9
30 24
40 34
50 39
60 40
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Q3
0
5
10
15
20
25
30
35
40
45
0 10 20 30 40 50 60 70
Cum
ulati
ve F
requ
ency
Number of Sockets
Cumulative Cumulative FrequencyFrequency
GraphsGraphs
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Quartiles
40 ÷ 4 =10
Q1
Q2
Q1 =21
Q2 =27
Q3 =36
New Term
Interquartile rangeSemi-interquartile range
(Q3 – Q1 )÷2 = (36 - 21)÷2=7.5
Quartiles fromQuartiles fromCumulative FrequencyCumulative Frequency
GraphsGraphs
Km travelled on 1 gallon (mpg)
Cumulative
Frequency
20 3
25 11
30 30
35 53
40 69
45 76
50 80
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0
10
20
30
40
50
60
70
80
90
0 10 20 30 40 50 60
Cum
ulat
ive
Fre
quen
cy
Km travelled on 1 gallon (mpg)
Cumulative Cumulative FrequencyFrequency
GraphsGraphs
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Q3
Cumulative Cumulative FrequencyFrequency
GraphsGraphs
Quartiles
80 ÷ 4 =20
Q1
Q2
=28
= 32
= 37
New Term
Interquartile rangeSemi-interquartile range
(Q3 – Q1 )÷2 = (37 - 28)÷2=4.5
Apr 21, 2023Apr 21, 2023
Now try Exercise 3Ch11 (page 166)
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Quartiles fromQuartiles fromCumulative FrequencyCumulative Frequency
GraphsGraphs
Apr 21, 2023Apr 21, 2023
Starter QuestionsStarter Questionsw
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11 28
2. Find the volume of a cone 15cm in height
and 10cm in diameter.
x x 21. Factorise
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1.1. Know the term Standard Know the term Standard Deviation.Deviation.
1. To explain the term and calculate the Standard Deviation for a collection of data.
Standard DeviationStandard DeviationS5 Int2
1.1. Calculate the Standard Calculate the Standard Deviation for a collection Deviation for a collection of data.of data.
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Standard DeviationStandard DeviationFor a FULL set of DataFor a FULL set of Data
The range measures spread. Unfortunately any big change in either the largest value or smallest scorewill mean a big change in the range, even though
onlyone number may have changed.
The semi-interquartile range is less sensitive to a single number changing but again it is only really
based on two of the score.
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S5 Int2
Standard DeviationStandard DeviationFor a FULL set of DataFor a FULL set of Data
A measure of spread which uses all the data is the
Standard Deviation
The deviation of a score is how much the score differs from the mean.
Score Deviation(Deviation)2
70
72
75
78
80
Totals 375
Example 1 :Find the standard deviation of these fivescores 70, 72, 75, 78, 80.
S5 Int2
Standard DeviationStandard DeviationFor a FULL set of DataFor a FULL set of Data
Step 1 : Find the mean
375 ÷ 5 = 75Step 3 : (Deviation)2
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-5
-3
0
3
5
0
25
9
0
9
25
68
Step 2 : Score - MeanStep 4 : Mean square deviation
68 ÷ 5 = 13.6
Step 5 :
Take the square root of step 4
√13.6 = 3.7
Standard Deviation is 3.7 (to 1d.p.)
Example 2 :Find the standard deviation of these sixamounts of money £12, £18, £27, £36, £37, £50.
S5 Int2
Standard DeviationStandard DeviationFor a FULL set of DataFor a FULL set of Data
Step 1 : Find the mean
180 ÷ 6 = 30
Apr 21, 2023Apr 21, 2023 Created by Mr. Lafferty Maths Dept.Created by Mr. Lafferty Maths Dept.ww
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Step 2 : Score - Mean
Step 3 : (Deviation)2
Step 4 : Mean square deviation
962 ÷ 6 = 160.33
Score Deviation(Deviation)2
12
18
27
36
37
50
Totals 180
-18
-12
-3
6
7
20
324
144
9
36
49
400
0 962
Step 5 :
Take the square root of step 4
√160.33 = 12.7 (to 1d.p.)
Standard Deviation is £12.70
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Standard DeviationStandard DeviationFor a FULL set of DataFor a FULL set of Data
When Standard Deviationis LOW it means the data values are close to the
MEAN.
When Standard Deviationis HIGH it means the data values are spread out from
the MEAN.
Mean Mean
Apr 21, 2023Apr 21, 2023
Now try Exercise 4Ch11 (page 169)
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Standard DeviationStandard Deviation
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Starter QuestionsStarter Questionsw
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10 2 - 5
2. Solve the simultaneous equations
x y and x y
1. Construct a cumulative frequency table
For the data below.
S5 Int2
Waist Sizes Frequency
28” 7
30” 12
32” 23
34” 14
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1.1. Construct a table to Construct a table to calculate the Standard calculate the Standard Deviation for a sample of Deviation for a sample of data.data.
1. To show how to calculate the Standard deviation for a sample of data.
S5 Int2
Standard DeviationStandard DeviationFor a Sample of DataFor a Sample of Data
2.2. Use the table of values to Use the table of values to calculate Standard calculate Standard Deviation of a sample of Deviation of a sample of data.data.
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Standard DeviationStandard DeviationFor a Sample of DataFor a Sample of Data
In real life situations it is normal to work with a sample of data ( survey / questionnaire ).
We can use two formulae to calculate the sample deviation.
2( )
1
x xs
n
s = standard deviationn = number in sample∑ = The sum of
22
1
xx
nsn
x = sample mean
We will use this version because it is easier to use in
practice !
Example 1a : Eight athletes have heart rates 70, 72, 73, 74, 75, 76, 76 and 76.
Apr 21, 2023Apr 21, 2023 Created by Mr. Lafferty Maths Dept.Created by Mr. Lafferty Maths Dept.ww
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S5 Int2
Standard DeviationStandard DeviationFor a Sample of DataFor a Sample of Data
Heart rate (x)
x2
70
72
73
74
75
76
76
76
Totals
4900
5184
5329
5476
5625
5776
5776
5776
∑x2 = 43842∑x = 592
Step 2 :
Square all the values and find the
total
Step 3 :
Use formula to calculate sample deviation
22
1
xx
nsn
259243842
88 1
s
43842 43808
7s
4.875s
2.2 ( 1 . .) s to d p
Step 1 :
Sum all the values
Q1a. Calculate the mean :
592 ÷ 8 = 74
Q1a. Calculate the sample deviation
Created by Mr. Lafferty Maths Dept.Created by Mr. Lafferty Maths Dept.
Heart rate (x)
x2
80
81
83
90
94
96
96
100
Totals
6400
6561
6889
8100
8836
9216
9216
10000
65218 64800
7s
418s
20.4 1 . .) ( s to d p
Example 1b : Eight office staff train as athletes. Their Pulse rates are 80, 81, 83, 90, 94, 96, 96 and 100 BPM
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Standard DeviationStandard DeviationFor a Sample of DataFor a Sample of Data
∑x = 720
22
1
xx
nsn
272065218
88 1
s
Q1b(ii) Calculate the sample deviation
Q1b(i) Calculate the mean :
720 ÷ 8 = 90
∑x2 = 65218
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S5 Int2
Standard DeviationStandard DeviationFor a Sample of DataFor a Sample of Data
Q1b(iii) Who are fitter the athletes or staff.
Compare meansAthletes are fitter
StaffAthletes
2.2 1 . .) ( s to d p
74 Mean BPM 90 Mean BPM
20.4 1 . .) ( s to d p
Q1b(iv) What does the deviation tell us.Staff data is more
spread out.
Apr 21, 2023Apr 21, 2023
Now try Ex 5 & 6Ch11 (page 171)
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S5 Int2
Standard DeviationStandard DeviationFor a Sample of DataFor a Sample of Data
Apr 21, 2023Apr 21, 2023
Starter QuestionsStarter Questionsw
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2
1. I f lines have the same gradient
What is special about them.
2. Factorise x +8x +15
3. Find the missing angles.
S5 Int2
33o
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1. To construct and interpret Scattergraphs.
1. Construct and understand the Key-Points of a scattergraph.
Scatter GraphsScatter GraphsConstruction of Scatter Graphs
2. Know the term positive and negative correlation.
S5 Int2
S5 Int2
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Scatter GraphsScatter GraphsConstruction of Scatter Graph
Team
100
120
140
160
180
0 20 40 60
Weight (kg)
Hei
ght
(cm
) Sam
Jim
Tim
GaryJoe
Dave
Bob
This scattergraph shows the heights and weights of a
sevens football team
Write down height and weight of each
player.
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Scatter GraphsScatter GraphsConstruction of Scatter Graph
xxx x
x x
Strong positive correlation
xx
x xx
x
Strong negative correlation
Best fit line
Best fit line
When two quantities are strongly connected we say there is a strong correlation between them.
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S5 Int2
Scatter GraphsScatter GraphsConstruction of Scatter Graph
Key steps to:Drawing the best fitting straight line to a scatter
graph1. Plot scatter graph.
2. Calculate mean for each variable and plot the coordinates on the scatter graph.
3. Draw best fitting line, making sure it goes throughmean values.
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0
2
4
6
8
10
12
0 2 4 6 8 10 12
Ages (Years)
Car
pri
ces
(£1000)
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Scatter GraphsScatter GraphsConstruction of Scatter Graph
Is therea
correlation?If yes, what
kind?
AgePrice
(£1000)
3
1
1
2
3
3
4
4
5
9
8
87
6
5
5
4
2
Strong negative correlation
Draw in the best fit line
S5 Int2
Mean Age = 2.9
Mean Price = £6000
Find the mean for
theAge and Prices values.
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Scatter GraphsScatter GraphsConstruction of Scatter Graph
Key steps to:Finding the equation of the straight line.
1. Pick any 2 points of graph ( pick easy ones to work with).
2. Calculate the gradient using :
3. Find were the line crosses y–axis this is b.
4. Write down equation in the form : y = ax + b
2 1
2 1
y ya
x x
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0
2
4
6
8
10
12
0 2 4 6 8 10 12
Ages (Years)
Car
pri
ces
(£1000)
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Scatter GraphsScatter Graphs
Pick points (0,10) and
(3,6)
y = 1.38x + 10
S5 Int2
Crosses y-axis at 10
10 61.38
3 0a
Apr 21, 2023Apr 21, 2023
Now try Exercise 7Ch11 (page 175)
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Scatter GraphsScatter GraphsConstruction of Scatter Graph
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Starter QuestionsStarter Questionsw
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2h - 49
1. Write the five figure summary for the data.
1, 1, 2, 3, 8, 3, 2
2. Factorise
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ProbabilityProbability
Learning IntentionLearning Intention Success CriteriaSuccess Criteria
1.1. Understand the probability Understand the probability line. line.
1. To understand probability in terms of the number line and calculate simple probabilities.
2.2. Calculate simply Calculate simply probabilities.probabilities.
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ProbabilityProbabilityLikelihood LineLikelihood Line
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10.50
CertainEvensImpossibleNot very
likelyVerylikely
Winning theLottery
School Holidays
Baby BornA Boy
Seeing a butterfly
In July
Go backin time
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ProbabilityProbabilityLikelihood LineLikelihood Line
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10.50
CertainEvensImpossibleNot very
likelyVerylikely
Everyone getting100 % in test
HomeworkEvery week
Toss a coinThat land
Heads
It willSnow in winter Going without
Food for a year.
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Apr 21, 2023Apr 21, 2023
ProbabilityProbability
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To work out a probability
P(A) = number of outcomes
Total number of possible outcomes
Probability is ALWAYS in the range 0 to 1
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We can normally attach a value to the probability of an event happening.
ProbabilityProbabilityNumber Likelihood Number Likelihood
LineLine
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10.50
CertainEvensImpossible
1 2 3 54 76 8
0.1 0.2 0.3 0.4 0.6 0.7 0.8 0.9
Q. What is the chance of picking a number between 1 – 8 ?
Q. What is the chance of picking a number that is even ?
Q. What is the chance of picking the number 1 ?
88
= 1
48
= 0.5
18 = 0.125
P =
P(E) =
P(1) =
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ProbabilityProbabilityLikelihood LineLikelihood Line
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10.50
CertainEvensImpossibleNot very
likelyVerylikely
Q. What is the chance of picking a red card ?
Q. What is the chance of picking a diamond ?
Q. What is the chance of picking ace ?
52= 0.5
1352
= 0.25452
= 0.08
26
0.1 0.2 0.3 0.4 0.6 0.7 0.8 0.9
P (Red) =
P (D) =
P (Ace) =
52 cards in a pack of cards
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Apr 21, 2023Apr 21, 2023
Apr 21, 2023Apr 21, 2023
Now try Ex 8Ch11 (page 177)
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Probability Probability
Apr 21, 2023Apr 21, 2023
Starter QuestionsStarter Questions
21. Factorise 16x - 36
2. The average price of a two wek holiday is £ 1000.
The prices depreciates @ 2% each year.
How much is the average price of a holiday
af ter 3 years.
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Apr 21, 2023Apr 21, 2023
Learning IntentionLearning Intention Success CriteriaSuccess Criteria
1.1. Know the term relative Know the term relative frequency.frequency.
1. To understand the term relative frequency.
2.2. Calculate relative Calculate relative frequency from data frequency from data given.given.
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Relative FrequenciesRelative Frequencies
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Relative FrequencyHow often an event happens compared
to the total number of events.
CountryCountry FrequencyFrequency Relative FrequencyRelative Frequency
FranceFrance 180180
ItalyItaly 9090
SpainSpain 9090
TotalTotal
Example : Wine sold in a shop over one week
180 ÷ 360 = 180 ÷ 360 =
90 ÷ 360 = 90 ÷ 360 =
90 ÷ 360 = 90 ÷ 360 =
360 360
0.25 0.25
0.25 0.25
0.5 0.5
1 1
Relative Frequency
always added up to
1
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Relative FrequenciesRelative Frequencies
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Relative FrequenciesRelative Frequenciesw
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BoyBoyss
GirlsGirls TotalTotal
FrequencyFrequency 300300 200200
Relative Relative FrequencyFrequency
Example Calculate the relative frequency for boys and girlsborn in the Royal Infirmary hospital in December 2007.
500
0.6 0.4 1
Relative Frequency adds up to 1
S5 Int2
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Now try Ex 9Ch11 (page 179)
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S5 Int2
Relative FrequenciesRelative Frequencies
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Starter QuestionsStarter Questionsw
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13, 19, 25, 25, 28, 32, 34, 36
2. The population of Scotland was 6 Million in 2000.
I t increased by 3% each year for 4 years.
What is the population after the 4 years.
S5 Int2
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Probability from Probability from Relative FrequencyRelative Frequency
Learning IntentionLearning Intention Success CriteriaSuccess Criteria
1.1. Know the term relative Know the term relative frequency.frequency.
1. To understand the connection of probability and relative frequency.
2.2. Estimate probability from Estimate probability from the relative frequency.the relative frequency.
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S5 Int2
Probability from Probability from Relative FrequencyRelative Frequency
ww
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handedness in a school. Results are given below
Number of Number of Left - Hand Left - Hand StudentsStudents
Total Total AskedAsked
RelativeRelative
FrequencFrequencyy
SeanSean 22 1010
KarenKaren 33 2525
DanielDaniel 2020 200200
Example 1
2 = 0.2
10
S5 Int2
Apr 21, 2023Apr 21, 2023
3 = 0.12
2520
= 0.1200
When the sum of the frequencies is LARGE the
relative frequency is a good estimate of the
probability of an outcome
Probability from Probability from Relative FrequencyRelative Frequency
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Number of Number of Alarmed Alarmed HousesHouses
Total Total AskedAsked
RelativeRelative
FrequencFrequencyy
PaulPaul 77 1010
AmyAmy 1212 2020
MeganMegan 4040 100100
Example 2
7 = 0.7
10
S5 Int2
Apr 21, 2023Apr 21, 2023
12 = 0.6
2040
= 0.4100
What is the probability
that a house is alarmed ?
0.4
Who’s results would you use as a estimate of the probability of a
house being alarmed ?
Megan’s
Three students carry out a survey to study how many houses had an alarm system in a particular area. Results are given below
Apr 21, 2023Apr 21, 2023
Now try Ex 10Ch11 Start at Q2
(page 181)
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S5 Int2
Probability from Probability from Relative FrequencyRelative Frequency