Descriptive Statistics - Graph Types

What is a chart?

A chart shows data in a more visual way. It can be helpful to illustrate smaller and larger differences between conditions.

What 5 graphs are explored in the course?

1 - Bar chart

2 - Scatter diagram

3 - Line graphs

4 - Histograms

5 - Pie charts

What are the key features of Bar charts?

• IV is shown along the base (x axis)

• DV is shown up the side (y axis)

• The height of the bars indicate the mean score

  • Each bar represents one condition of the IV

• Bars are separate, they don’t touch

What are the key features of Scatter diagrams?

• Used to show correlations

• Variable 1 goes along the x axis while Variable 2 goes up on the y axis

• You plot the points and each one represents a participant or case

• Draw a line of best fit if requested to do so

What are the key features of Histograms?

• These represent the data distribution far more accurately.

• The x axis shows a group of continuous data values

• The y axis shows the frequency density instead of the raw frequency value.

• The bars in a Histogram graph do touch

• The area of each bar - height X width - is equal to the frequency

What are the key features of Line graphs?

• They display continuous data

• The x axis is usually a time frame/ period

• The y axis is the measured value or frequency

• You then plot the points and use straight lines to join the plotted points

• If there’s 2 parts to the DV, colour code them and add a key

What are the key features of Pie charts?

• These use percentages and angles to represent segments of a circle as the values associated with data groups

• You must figure out the angles for each segment as well as the percentage for each

• Ensure that when labeling, you add both the percentage and angles as well as the label for each segment

Within histograms, how does one calculate the frequency density?

To calculate the class width, do the Upper bound (largest) class interval MINUS Lower bound of class interval

To get all 4 marks/ full marks in these graph questions, what must you do?

• Always add title ( 1 mark)

• Always label both the x and y axis, or the segments if its a pie chart

• Always plot the points correctly

• Use the appropriate graph type

• Add a reasonable scale