Presenting Data Graphically Flashcards
at are the different ways to present data graphically?
Bar charts
Scatter diagrams
Histograms
Line graphs
When are bar charts used?
To represent discrete data where the data is in categories, which are placed on the x axis
What is on the x and y axis of bar charts?
X axis - the catagories
Y axis - mean or frequency
When drawing a bar chart what do you need to keep in mind?
Columns don’t touch and they have equal width or spacing
What is the difference between a bar chart and a histogram?
Bar charts present discrete data where else histograms present continuous data
When are scatter diagrams used?
For measuring the relationship between 2 variables
What do you need to keep in mind when drawing a scatter diagram?
Data from 1 variable is on 1 axis whilst data from the other variable is on the y axis
You plot an x on the graph where the 2 variables meet
The patterns of the plotted points may then reveal a correlation
Which type of data do histograms present?
Why?
Continuous data because they present data on a continuous scale
What do you need to keep in mind when drawing a histogram?
Columns touch because each one forms a single score (interval) on a related scale
These scales (intervals) are placed on the x axis
The height of the column shows the frequency
When may a line graph be used?
To present continuous data
What do line graphs show?
They show where the mid point of each column on a histogram would be
What are line graphs useful for?
To present continuous data, between two possible variables
Define correlation?
When 2 or more variables (co-variables) are measured in order to identify if there is a relationship between then
How do you measure correlation
A single numerical value (PMCC or r)
What are the 3 types of correlation?
Positive
Negative
No correlation
What is happening to the variables in positive correlation?
Draw a graph showing positive correlation?
What is happening to the variables in negative correlation?
Draw a graph showing negative correlation?
What is happening to the variables when there is no correlation?
Draw a graph showing no correlation?
What is the correlation co-efficient?
A number between -1 and 1
As r tends towards -1 it means that the data is getting stronger negative
As r tends towards 1 it means that the data is gettibng more strong positive
R=0 there is no correlation
What is important to remember about correlation?
You can’t state a cause and effect by using correlation
What are the advantages of using correlation?
They can be used when it would be unethical/ unpractical to conduct an experiment
If correlation is significant, then further investigations are justified
If correlation is significant, you can rule out a casual relationship
What are the disadvantages of using correlation?
Correlation analysis can’t demonstrate a cause and effect relationship between variables
There may be other unknown variables that can explain why the co-variables being studied are linked
Extraneous variables may lead to false conclusions
What is an example of a famous piece of research?
Milgriam’s variation using LOC and obedience scores
Why do we add 1 after calculating the range?
To avoid rounding errors
