Data representation

• What is discrete data

  data that can be placed into separate categories e.g number of people/participants
• What is continuous data

  data that cannot be placed into distinct categories and can be presented on a number line e.g height of students in a class, time taken to complete race, weight
• How to choose an appropriate graph

  discrete data = bar charts (6 or more categories), pie charts (less than 6 categories)

  continuous data = line graphs (shows change overtime - usually time), scatter graph (shows relationships/correlations), histograms (inequalities <,>)
• Features of a bar chart

  used for discrete data

  columns DON'T TOUCH

  useful for comparing groups of data

  used for categories

  the mean/frequency on Y axis

  the category on X axis
• Features of pie charts

  used for discrete data

  shows relative contribution to overall total (proportions)

  useful when data is showing a %

  requires data to be represented as an angle

  TITLE NECESSITY: A pie chart to show the proportions of...
• Features of line graphs

  used for continuous data - usually time

  useful for comparing 2 or more conditions

  good for looking at changes overtime

  continuous scale on X axis

  frequency/measurement on Y axis

  data point are connected with straight line from point to point
• Features of scatter graph/diagram

  used for continuous data

  used for measuring the relationship between 2 variables (a correlation)

  data from one variable is presented on Y axis and other on X - doesn't matter which way around

  shows a positive, negative or no correlation

  TITLE NECESSITY: A scatter graph to show the relationship between...
• Features of a histogram

  used for continuous data

  columns touch

  area of the column shows the frequency

  frequency density is on the y axis

  width of bar on the x axis

  frequency density = frequency/class width

  TITLE NECESSITY: A histogram to show the frequency density of (x axis)... e.g the ages of 25 children
• Histogram example

  
• TIP: fully operationalise axis
• For each graph you must remember 4 things:

  1. title
  2. labels on axis
  3. appropriate scale
  4. drawn correctly (e.g. bars with gaps)
• How to decide which graph to use

  • is it a relationship/correlation? yes = scatter graph
  • is the data group with inequalities? yes = histogram
  • is the data changing overtime? yes = line graph
  • are there more than 6 categories? yes = bar chart
  • are there less than six categories? yes = pie chart