Data Analysis Techniques

Descriptive Statistics

Measures of Central Tendency

Mean = the sum of the scores / the number of scores

- = skewed by the extremes

Median = the middle of an ordered list

- =  does not take into account the extremes

Mode = the most occuring number

Bimodal = Two modes


Measures of Dispersion


Range = highest score - lowest score


Standard Deviation =

Small S.D. = scores close to the mean
Large S.D. = far from the mean






Correlation =

- a statistical relationship between two or more variables (anything that can change such as IQ, temperature etc)


- Two variables = co-variates


Positive

Negative

Advantages 
- useful when an experiment is impractical or unethical
- helps prove if it's worth investigating further


Disadvantages 
- cannot tell cause and effect only hints at a relationship... lacks power and rigour of experiment






Presenting Data

Scattergrams

- display results of correlation.
- quick visual impression
- each point on the graph is the point where the scores of the two variables names on the axes cross.
- looking at the general spread of the points tell us the extent the two variables relate.


Tables

Bar Chart

- good when different sets of scores need comparison
- discrete data


Histograms

Don't get confused with Histograms and Bar Charts!
Histograms have history so they stick together. Bar charts are barred from seeing each other. 

Frequency Polygons

- A dot will be placed at the top of a bar or histograms highest point, and connected with a line


Percentages

- Tables, bar charts, histograms, pie charts
- If you scored 43 out of 89 in a test you divide 43 by 89, which equals 0.48. You then multiply 0.48 by 100 = 48%.

Pie Charts

- Visual impression of different proportions which various groups of participants share
- segmants represent a percentage