Populations and sampling

What is a population?

All items of interest.

What is a census?

Measures / observes all members of a popultion.

What is a sample?

Selection / observations taken from a subset to find out information about the population as a whole.

Positives and negatives of a census

+Accurate

-Time consuming

-Expensive

-Hard to ptocess

Positives and negatives of a sample

+Less time consuming

+Cheaper

+Less data to process

-Less accurate

-Sample may not be big enough to represent

What is simple random sampling?

Using a random number generator / names on paper.

What is systematic sampling?

Choose first item randomly, then every nth item after.

What is stratified sampling?

Proportion of each category and randomly select from each.

What is quota sampling?

Selects the sample based on characteristics so it represents the whole population.

What is opportunity sampling?

Taking the sample from those available at the time and who fit the criteria.

What is quantitative data?

Using numbers.

What is qualitative data?

Not using numbers.

What is continuous data?

Any value in a range.

What is discrete data?

Only specific values.

What UK cities do we need to know and where are they?

• Leuchars- North

• Leeming- Midlands

• Heathrow- London

• Hurn- South

• Cambourne- South West

What international cities do we need to know and where are they?

• Jacksonville- US South East coast

• Beijing- China

• Perth- Australia South West coast (only one in Southern Hemisphere)