# Statistics equations Flashcards

What is a population?

The whole set of items that are within interest (eg. group of people, apples in a basket)

What is a census?

An observation of every member within a population

What is a sample?

A selected subsection of members from a population (in order to gather info about the whole population)

What is a sampling frame?

A list of individually written/ numbered sampling units

What are the advantages of a sample compared to a census?

A sample is much more efficient and less time consuming than a census, however it may not be as accurate. (A census may also destroy all items in a population which would lead to no items being left to be sold)

What is a simple random sample?

A sample where every member has an equal chance of being selected

What is systematic sampling?

Where samples are taken at regular intervals from an ordered list

What is stratified sampling?

Where a population is divided into mutually exclusive strata (groups of similarity, eg female group and male group) then a random sample is taken from each stratum (from each group)

What is random sampling?

When a sample of the population is chosen at random to remove any bias

What is quota sampling?

When a sample is taken of members that reflect on the whole population

What is opportunity (convenience) sampling?

When a sample is taken from members of a population that are available at the time who fit the criteria

Compare random to non-random sampling

Random sampling allows for the bias to be removed, whereas non-random sampling produces a bias that wont represent the population accurately

What are the types of data and state what each one consists of

Numerical - quantitative (numbers)

Non-numerical - qualitative (adjectives such as colours/ names)

Continuous - any values within a range (time can be 2s or 3.75s / decimal values)

Discrete - specific values within a range (5 girls or 7 boys / exact values)

What is the class width?

The difference between the lower and upper class boundaries

What are all the mean variables you can get on a large data set?

Temperature / wind direction and wind speed (with Beaufort scale)/ cloud coverage / visibility / pressure