Stats A level maths

qualitative data can be described using

Words

Quantitative data can be described using

Numbers

Discrete data is…

Data that can only take specific values

Continuous data is…

Quantitative data that can have any value within a specific range

Population is a

Whole set of the thing u are interested in

Advantages of using a sample rather than a population

Quicker, easier and cheaper

Disadvantages of using a sample rather than a population

Might not fully represent the population and may introduce bias

A sampling frame is

A list of all the members of a population

Population parameter is a…

Numerical value describing a characteristic of the population

Statistic is a

Estimate of a population parameter using data from a sample

Random sampling is

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

Biased sampling is..

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

Simple random sampling is..

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

Method of simple random sampling..

Uniquely number every member of a population and randomly different numbers using a random number generator

Pros of simple random sampling

Unbiased sampling method. Quick for a small population or if you want a small sample

Disadvantages of a simple random sample

Time consuming for a large population and cannot be used if not possible to number or list all members. Sampling frame needed

Systematic sampling is

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

Advantages of systematic sampling

Useful when there is a natural order. Quick and easy to use for large populations and samples

Disadvantages of systematic sampling

The list needs to be in a random order to avoid bias. A sampling frame is needed

stratified sampling is..

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

How to do stratified sampling

Size of sample divided by size of population x number of members in the group

Advantages of stratified sampling

Useful when there are very different groups in a population, the sample will be representative of the populations structure. The members selected are chosen randomly

Disadvantages of stratified sampling

Cannot be used if it is not possible to split the population into specific groups. Same disadvantages of simple random sampling

cluster sampling is..

The population is separated into clusters. And a random selection of clusters are sampled

How to cluster sample

Split population into clusters, randomly select which clusters are included in the sample

Advantages of cluster sampling

Easy to carry out, can produce large samples

Disadvantages of cluster sampling

Can introduce bias as there will be variability between clusters

Opportunity sampling is..

A sample is formed using available members of the population who fit the criteria

How to opportunity sample

Select that are easiest to reach

Advantages of opportunity sampling

Quick and easy to perform, useful when a list of the population is not possible

Disadvantages of opportunity sampling

Unlikely to be representative of the populations structure, likely to produce biased results

quota sampling is..

The population is split into groups and members of the population are selected until each quota is filled

How to quota sample

Calculate how many members are needed form each group and select members from the population until each quota is filled

Pros of quota sampling

Sample will be representative of the populations structure, useful when a sampling frame is not available

Disadvantages of quota sampling

Can introduce bias as some members of the population may choose not to be included in the sample

What is a census?

Observers of measures every member of a population

What is a sample?

A selection of observations taken from a subset of the population which is used to find out information about the population

Advantages of a census

It should give a completely accurate result

Disadvantages of a census

Time consuming and expensive, cannot be used when the testing process destroys the item, hard to process large quantity of data