Data is collected and then processed. It can be displayed using graph and listed in tables. Calculations can be made to summarise the data. Finally the data is presented, discussed and conclusions are made.
Statistics are often used to help to show or prove something. When this happens an investigation or survey is often carried out.
Designing a Statistical Investigation
You may be asked to carry out an investigation or survey. The information below may help.
The collection of data
The collection of data takes time and is therefore expensive.
Choosing a sample
A sample must be evenly spread over the population. Choosing a random sample, where evey item has an equal chance of being chosen, helps to remove bias.
Bias occurs when a sample does not accurately represent the group from which it is taken.
There are several ways to obtain a random sample:
Questionnaires and Interviews
A questionnaire is a form used to obtain information. Careful preparation of questionnaires is essential and may require special training. Questionnaires can then be sent to people, which often results in a low return rate. Interviewers can be used to stop people in the street or to ring people to ask the questions. Surveys using these kinds of techniques can often produce biased samples unless they are well designed.
Organising and displaying the data
Analysis of the data
Calculations can be made and statistics such as the mean, median, mode and range can be found. See Topic 45.
Finally, and most importantly, the data, tables, graphs and calculations can be analysed and the results of a survey presented, summarised and any conclusions drawn.
As you can see, there is a lot to statistics.