Exploring DATA with graphs

Question 1

What 7 properties does a good graph have?

Answer 1

1. Shows the data
2. Induce the reader to think about the presented data
3. Avoid distorting data
4. Present many numbers with minimum risk
5. Make large data sets coherent
6. Encourage the reader to compare different pieces of data
7. Reveal the underlying message of the data

Question 2

Name 4 graph building guidelines

Answer 2

1. If plotting two variables, never use 3D plots
2. Do not use unnecessary patterns in the bars
3. Do not use cylinder shaped bars if it is not functional
4. Properly label the x and y axis

Question 3

Name and describe the four types of histograms

Answer 3

1. Simple histogram: visualise frequencies of scores for a single variable
2. Stacked histograms: compare relative frequencies of scores across groups
3. Frequency polygon: The same as a simple histogram, but uses a line, instead of a bar
4. Population pyramid: Comparing distributions across groups and the relative frequencies of scores in two populations

Question 4

What is a box plot? give another name for it?

Answer 4

A box-plot or box-whisker diagram uses the median as the centre of the plot. It is surrounded by the quartiles which show 25% and 75% of the data.

Question 5

Name the three types of box plot diagrams

Answer 5

1. 1-D boxplot- simple box plot for all scores of the chosen outcome
2. Simple boxplot- multiple boxplots for the chosen outcome by splitting the data by a categorical variable
3. Clustered boxplot- A simple boxplot, but it splits the data by a second categorical variable

Question 6

Do bar charts often utilise the mean, median or mode?

Answer 6

Mean

Question 7

What eight different types of bar charts are there?

Answer 7

1. The means of scores across different groups or categories
2. Clustered bar chart- Different coloured bars to represent levels of a second grouping variable
3. Stacked bar- clustered bar, but the bars are stacked
4. Simple 3-D bar-Second grouping variable is represented by an additional axis
5. Clustered 3-D bar- a clustered bar, but an extra categorical variable can be added on an extra axis
6. Stacked 3-D bar- a 3-D clustered bar, but the bars are stacked
7. A simple error bar- a simple bar chart, but there is no bar, but a line and dot
8. clustered error bar- clustered bar chart, but a dot with an error band around it

Question 8

What are line charts?

Answer 8

Bar charts with lines instead of bars

Question 9

What two types of line charts are there?

Answer 9

1. Simple line- the means of scores across different groups of cases
2. Multiple lines- This is equivalent to the clustered bar chart

Question 10

What is meant by a scatterplot

Answer 10

A graph that plots each person’s score on one variable against their score on another

Question 11

What 8 types of scatter plot are there?

Answer 11

1. Simple scatter- A scatterplot of one continuous variable against another
2. Groups scatter- Display points belonging to different groups in different colours
3. Simple 3-D scatter- a scatterplot of one continuous variables against two others
4. Grouped 3-D scatter- A scatterplot of one continuous variable against two others but displays different groups in different colours
5. Summary point plot- A bar chart, but there is a dot instead of a bar
6. Simple dot plot- A histogram, but instead of a summary bar representing frequency scores, individual scores are represented as dots
7. Scatterplot matrix- A grid of scatterplots showing the relationship between multiple pairs of variables in each cell of the grid
8. Drop-line- A clustered bar chart but a dot represents a summary statistic instead of a bar and a line connects the summary of each group

Question 12

How is an outlier decided in a box plot?

Answer 12

Any score greater than the upper quartile plus 1.5x the IQR

Question 13

How does spss mark an extreme score and an outlier in box plots?

Answer 13

circle- outlier

Asterix- extreme score