Graphs and correlations Flashcards
What are the types of graphs?
Bar chart
Line graph
Scattergram
Histogram
Bar chart
Pie chart
what are bar charts (Nominal and Ordinal)?
Bar charts show data in the form of categories to be compared, like male and female scores concerning chocolate consumption.
Categories are placed on the x-axis (horizontal) and the columns of bar charts should be the same width and separated by spaces.
The use of spaces illustrates that the variable on the x-axis is not continuous (for example, males do not at some point become females and vice versa).
Bar charts can show totals, means, percentages or ratios and can also display two values together, for example male and female consumption of chocolate as shown by gender and age.
What are histograms (Interval)?
Histograms and bar charts are somewhat similar, but the main difference is that histograms are used for continuous data, such as test scores.
The continuous scores are placed along the x-axis, while the frequency of these scores is shown on the y-axis (vertical)
There are no spaces between the bars since the data are continuous and the column width for each value on the x-axis should be the same width per equal category interval.
What are line graphs (Interval)?
A line graph is similar to a histogram in that the data on the x-axes are continuous.
The graph is produced by drawing a line from the mid-point top of each bar in a histogram. The advantage of a frequency polygon is that two or more frequency distributions can be compared on the same graph.
What are pie charts (Nominal)?
Pie charts are used to show the frequency of categories as percentages.
The pie is split into sections, each one of which represents the frequency of a category.
The sections are colour coded, with an indication given of what each section represents and its percentage score.
What are scattergraphs (Correlation)?
Display two sets of data to see if there is a relationship or connection.
What graph would be used for ‘The change in a person’s body temperature over the course of a day.’?
Line graph or histogram (temperature is interval data)
What graph can be used for ‘The difference in average annual rainfall between Manchester and Paris.’?
Bar chart (Manchester and Paris are categories).
What graph can be used for ‘The relationship between daily temperature and people’s ratings of how happy they are.’?
Scattergram (because it is correlational data)
What graph can be used for ‘The frequency of people who chose ‘snow’ as their favourite weather condition broken down into sub-categories of age.’?
Pie chart (snow is a category, and it is looking at frequency)
What is a correlation?
A correlation looks at the relationship between two variables.
What are the two types of correlation?
Positive: when one variable increases the other variable increases.
Negative: when one variable increases and the other decreases.
How can a correlation be presented?
Correlations can be presented graphically on a scattergraph.
Correlations can be presented statistically using the Spearman’s rank correlation coefficient.
What is an example of a positive and negative correlation?
Positive: The more time a child spend in daycare the more aggressive they are.
Negative: The more time a child spends in daycare the less they are attached to their mothers.
What is a correlation coefficient?
The correlation coefficient is the figure that is calculated after conducting a Spearman’s rank test. Statistical tests are used to enhance the accuracy of our correlations.
