Block 2

1
Block 2
By Rahul B
This PowerPoint presentation will help you to
revise for the GCSE Statistics exam this summer
with important notes on Block 2. It will help you
to remember key facts in the build up to your
exam.
2
Introduction

• In this presentation, you will revise the
  following
• Stem and Leaf Diagrams
• Cumulative Frequency
• Outliers
• Shape of Distribution
• Weighted Mean
• Standardised Scores

3
Comparative Pie Charts
Firstly, draw two normal pie charts. They should
both be the same size. You need to know how much
is being represented by each chart so work out
the radius of both. Write the two frequencies as
ratios. Square root the ratio. Multiply the
bigger radius by the smaller answer.
4
Stem and Leaf Diagram

• This diagram is easy to understand and draw.
  Heres the stem and leaf checklist
• Write a title
• Draw a key
• Put each row in order
• Align all numbers vertically
• Draw the diagram neatly
• Continue for example

5
Stem and Leaf Diagram - Examples
 
6
Cumulative Frequency Chart
This column is a running total of the frequency
column
7
Outliers

• When you have a large set of data, the chances
  are that there will be some unreliable data.
  These are called outliers. Heres how you find
  them
• Find the Upper Quartile and Lower Quartile of
  your data
• Do Upper Quartile-Lower Quartile to find the
  Inter Quartile Range
• Multiply the Inter Quartile Range by 1.5
• Any number below (Lower Quartile-Answer) or
  above (Upper QuartileAnswer) is an outlier.
• Continue for example

8
Outliers - Example
Lets say your data has an Upper Quartile of 157
and a Lower Quartile of 139. 157-13918. 18 is
the Inter Quartile Range. 181.5 27. 139-27108.
Any number below 108 is an outlier. 13927166.
Any number above 166 is an outlier.
9
Shape of Distribution
Learn this chart. Everything in the middle yellow
section is average. As the chart goes left, it is
getting below average. As the chart goes right,
it is getting above average.
10
Weighted Mean

• Follow the following steps to find the weighted
  mean
• Know the number and weight of what you are
  studying
• Add up the numbers and weights
• Divide the numbers by the weights
• The answer is the weighted mean
• Continue for example on weighted mean

11
Weighted Mean - Example
Coursework67 weight of 4 Written
84 weight of 10 Listening 90 weight of
6 (674)(1084)(690)/41061648/20 1648/2082.
4 82.4 is the weighted mean.
12
Standardised Scores

• This is the easiest thing you will come across in
  Block 2. The following steps will teach you how
  to do it
• Work out the value, mean and standard deviation
  of your data
• Do the Value-Mean
• Do the Answer-Standard Deviation
• That is the final answer.
• 0 is average, above 0 is above average and below
  0 is below average.
• Continue for an example

13
Standardised Score - Example
Jim got 106 in his test, the class mean is 100
and the standard deviation is 10. 106/1001.06 1.0
6/100.11 Jims standardised score is 0.06, just
above average.