Data Handling

1
Data Handling

• Analysing and Interpreting Data

2
Introduction

• Getting your data
• Types of data
• What can the data show?

3
Primary or Secondary?

• Primary data is data you collect yourself, such
  as a survey, or a set of measurements
• Secondary data is data which someone else has
  already collected, which you want to use

4
Types of Data

• There are two kinds of data
• Non-numerical, or qualitative data, such as
  colours, brand names
• Numerical, or quantitative data, such as the
  number of bottles (how many?), or a measurement
  (how long?)

5
Qualitative Data

• Non-numerical or descriptive data
• e.g. your favourite radio station
• Which of these are non-numerical?
• The colour of Aston Villa shirts
• The number of men in the team
• The length of the football pitch

6
Quantitative Data

• Numerical data
• e.g. the number of brothers you have
• Which of these are numerical?
• The colour of your mobile phone
• The number of calls you made yesterday
• The time you spent on your last call

7
Types of Quantitative Data

• Discrete data is separate values, e.g. how many
  brothers, what shoe size
• Continuous data is measured on a continuous
  scale, e.g. length, weight, time

8
Which type are these?

• The number of phone calls you made yesterday
• The amount of time you spent on the phone
  yesterday
• Your height
• The number of customers in a shop during an hour

9
Summary

• Data is of two main types
• Qualitative or descriptive, non-numerical
• Quantitative or numerical
• Quantitative data is of two kinds
• Discrete separate, usually whole numbers
• Continuous measurements, often decimals

10
Charts

• Data is often represented using charts, such as
  bar charts, pie charts and pictograms
• These are mainly used for qualitative data, and
  discrete quantitative data, which comes in
  ready-made groups

11
Bar Charts and Pie Charts

• A bar chart is used to compare the number of
  times values occur within a set of data
• A pie chart is often used to show how values are
  shared out in a group of data

12
Averages

• Mean total of values, divided by number of
  values
• Median is middle value, when values are arranged
  in order of size
• Mode is the value which occurs most often (there
  may be more than one mode, or none at all)

13
Averages

• The average of a group of data items gives you a
  typical value
• It tells you how large the values are, on
  average
• Averages are used to compare sets of data

14
Range (Dispersion)

• The range of a set of data is
• The largest value minus the smallest value

15
Dispersion

• The range of a group of data shows how spread
  out the data is
• If the range is small, the data are close
  together
• If the range is large, the data are very spread
  out there is lots of variation

16
Qualitative Data

• You cannot find the mean or median of
  non-numerical data
• You cannot find the range of non-numerical data
• There may be one or more modes of non-numerical
  data

17
Summary

• Charts are used to display sets of data
• Averages and ranges are used to compare sets of
  data