Maths - Owen Shepherd

Role of a in quadratic

Control the width and direction of quadratic

Higher = steeper

Role of b in a quadratic

Control the axis of symmetry

Where it is reflected

Role of c

Y intercept

Sampling methods

Census, Sampling

Census sampling sampling methods

Simple random sampling, systematic, stratified, quota

Sample sampling methods

Opportunity (Convenience sampling)

Simple random sampling

Every person allocated a number (1-n), random numbers selected, Draw numbers until sample size is met

Simple random sampling pros and cons

Pros: Not biased - random spread

Cons: Time consuming, whole population needed, difficult to set up and manage

Systematic sampling

The whole population is sampled at regualr intervals,

Number 1-n, select every 5th number etc, until sample size is met

Systematic sampling pros and cons

Pros: Easy to set up, likely to be unbiased

Cons: Whole population needed, if the sleection interval coincide with a pattern it is biased

Stratified sampling

Population divided into groups of similar characteristic, same proportion taken from each group

Groups are called strata

Group data, split into groups, fine relevant number from each group for sample size

Stratified sampling pros and cons

Pros: If categories are mutually exclusive gives a good representation, useful when results differ

Cons: The process to select who to select and in what proportion can be difficult and inefficient

Cluster sampling

Population divide into distinct groups, randomly select a group of people to sample

Cluster sampling

Pros: Can be easy, More practical

Cons: Risk of bias in the group, could be less representative

Opportunity / convenience sampling

Sample chosen from a section of the population mose convenient for the sampler

e.g. the first people they see

Opportunity / convenience sampling pros and cons

Pros: Data gathered easily and quickly

Cons: There is no method to remove bias, could be not representative

Quota sampling

Sampler is given a quota of data from each group of x they need to collect

e.g. 3 male and 2 female

Quota sampling pros and cons:

Pros: It is easy for the interviewer, access select groups

Cons: Can be biased, groups excluded

Volunteer sampling

People choose to be part of the sample

Volunteer sampling pros and cons

Pros: Little time and effort, encourage engagement

Cons: Can be a lot of bias, people volunteer with strong oppinions