Types of data - Applied maths Statistics

What is the definition of a census

A census collects data about all the members of a population

What is the main advantage of a census

Gives fully accurate results

What are the disadvantages of a census

• time consuming

• Expensive

What are the advantages of sampling

Quicker and cheaper than census

Less data needs to be analysed

What are the disadvantage of sampling

Might not represent the population accurately

Can introduce bias

What are the 5 types of sampling

Simple random, systematic, stratified, quota and opportunity (convince)

What is the definition of random sampling

Every member of a group has an equal chance of being selected

What is the definition of Biased sampling

A sampling method from which misleading conclusions about the population could be drawn

What is the definition of Simple random sampling

Every possible sample of size n has an equal chance of being selected as the sample

Describe the method for simple random sampling

• uniquely number every member of a population

• Randomly select n different numbers using a random number generator

What are the pros of simple random sampling

• unbiased

• Quick for a small population when you want a small sample

What are the cons of simple random sampling

• time consuming for large population

• Can’t be used if not possible to number all members

What is the definition of Systematic sampling

A sample is formed by choosing members of a population at regular intervals using a list

What is the method for systematic sampling

Calculate the size of the interval ‘k’

Choose a random starting point between 1 and ‘k’

Select every kth member after the first one

What’s the equation for calculating the size of the interval for systematic sampling

Size of population (N) / size of sample (n)

What are the pros of systematic sampling

Useful when there is a natural order

Quick and easy for large populations and samples

What are the cons of systematic sampling

List needs to be in a random order to avoid bias

A sampling frame is needed

What is the definition of stratified sampling

The population is divided into specific groups and a random sample is taken from each

What is the method for stratified sampling

Calculate the number of members sampled from each group

Take a random sample from each group

What are the pros of stratified sampling

• useful when different groups in a population

• Sample will be representative of the population structure

• Members are chosen randomly

What are the cons of stratified sampling

Can’t be used if it is not possible to split the population into groups

Time consuming for large population

Can’t be used if you can’t number all members