Data collection

The type of data collected and how the associated sampling takes place depend on the statistical question asked.

There are a number of aspects of data collection that need to be considered when carrying out a statistical investigation.

Choose the questions (e.g. "Do you like …?", "How tall is …?") that will determine the type of data collected (e.g. categorical, numerical).
Choose a sample size that will allow confidence in the conclusion.
Use repeated sampling to demonstrate how much variation occurs in samples of different sizes.
Avoid bias in data collection.
Explore sources of bias in various contexts where data are collected.
Understand the importance of random selection.
Explore various methods of random sampling.
Know the relationship between samples and populations.
Learn to define populations and samples in various statistical contexts.

Types of data

The type of data collected depends on the type of question that is asked.

Generally speaking, as the sample size increases the information from the data becomes more reliable.

Bias in data can distort all results gained from statistical investigation.

It is important to make a distinction between the population, sample and a case.