“ We are just statistics, born to consume resources” - Horace (65-8 BC Epistles Book 1)
When information for a statistical investigation is collected and recorded this is referred to as data.
What is a statistical investigation?
There are four processes involved in a statistical investigation
1 Collection of data (information)
Data for a statistical investigation can be collected from records, from surveys, by direct observation or by measuring or counting. Data can be collected for the whole population, which generally means all the people of things that the conclusions of a statistical investigation would apply to, or for a sample of the population.
2 Organisation and Display of Data
This involves organizing data into tables and/or displaying the data with a suitable graph so that some of the features of the data are more visible. For the two types of data that we study in detail (categorical and numerical) there are appropriate tables and graphs.
Discrete data can be displayed by:
There are some statistics that are universally used to describe a set of data.
Calculating statistics that indicate the centre of the data and the spread of the data give us a picture of the sample or population under investigation.
Reading : http://www.mste.uiuc.edu/hill/dstat/dstat.html
4 Interpretation of Statistical Data
This process involves explaining the meaning of the table, graph or descriptive statistics in terms of the variable or theory to be investigated.Some questions that you may ask to interpret statistical data:
Types of data
Examples of categorical variables are:
- Colour of eyes : the categories would be blue, brown, hazel, green, violet
- Gender : Male or Female
- Marital Status : Single, Married, Separated, Divorced
A numerical value is recorded for this type of variable. The information collected is called numerical data.
- The number of people in a household : the variable could take the values 1, 2, 3, 4, …
- The weight of new born babies : the variable could take any value on the number line but it is likely to be in the range of 0.5 kg to 8 kg.
- The score out of 30 on a test : the variable could take the values 0, 1, 2, …, 30