Chapter 1 applied - populations and samples

Census

Data collected from every member of the entire population

Advantages of a census

Should give a completely accurate result

Disadvantages of a census

Time consuming, expensive,

Can't be used when testing involves destruction

Large volume of data to process

How do you carry out a systematic sample?

Find k= population size / sample size

Start at a randomly selected item between 1 and k

Every kth value after that becomes the sample

How do I take a stratified sample?

The population is divided into strata

To find how many people need to be sampled in each strata representing the proportion of that strata in the population - (no. In stratum/no. in population) × sample size needed from whole pop

a simple random sample is carried out from a sampling frame of the group

How is a quota sample carried out?

The population is divided into groups based on a characteristic

A quota of items from each group is set to represent the groups proportion in the population

What is opportunity/convenience sampling?

The sample is selected from people available at the time of study who meet criteria

How do you take a simple random sample?

An identifying number is allocated to each item in the sampling frame

A random number generator is used to select the items from the sampling frame with the corresponding number.

What's discrete data?

Can only be specific values

What's continuous data?

Can be any decimal value in a specified range