Visualising Data

Question 1

Why is statistical analysis useful?

Answer 1

• Allows us to describe existing data and to discover patterns in the data
• Allows us to make inferences about a population based on a sample from that population

Question 2

Describe bar charts

Answer 2

• Appropriate for data on a categorical or ordinal scale
• They display the number of times each category occurs in the data
• All the same width and separate
• Several variations: grouped bar charts, stacked bar charts

Question 3

Describe pie charts

Answer 3

• Appropriate for data on a categorical or ordinal scale
• Illustrate the relative proportion of data in each category (not absolute)
• Capture part-whole relationships (different slices add up to meaningful whole)
• Most useful when there are only a few categories and the differences among these categories are fairly large

Question 4

Describe histograms

Answer 4

• Appropriate for data on an interval or ratio scale
• Data collected into bands, shows frequency with which values occur in the data
• Choice of the number and width of the bars drastically affect the appearance of the histogram

Question 5

Describe boxplots

Answer 5

• Appropriate for data on an interval or ratio scale
• Depict median, IQR, range of data
• Explorative stage of data analysis

Question 6

Describe scatterplots
(bivariate chart)

Answer 6

• Visualise the relationship between two variables

- Define each point in a dataset by 2 values (from the two variables of interest) and plot each point on a pair of axes

Question 7

Describe line graphs

bivariate chart

Answer 7

• Display relationship between 2 variables, usually between time on x axis and some other variable on the y axis
• Trend over time