Data collection Flashcards
Define a population
The whole set of data that is of interest
Define a Sample
The subset of the population intended to represent the population
Define a sampling unit
Each individual thing in the population that can be sampled.
Define a sampling frame
sampling units in a population being individually numbered to form a list.
what are the two types of sampling a population?
Census and Sample
define a sample
a subset of the population that is intended to represent the whole population
Define a census
An investigation of the whole population
what are the pros and cons of a census
Pros:
- gives a reliable and accurate result, representing the whole population
Cons:
- very time-consuming and expensive.
- a lot of data to process
- can’t be used for testing when the process destroys the item.
What are the pros and cons of a sample?
Pros:
- less costly and time-consuming
- More manageable bits of data.
- fewer people have to respond
Cons
- may not be representative of the whole sample
- sample size might not be large enough- so maybe not reliable
- might be less accurate.
what are the types of sampling methods
- simple random
- systematic
- opportunity
- quota
- stratified
What is simple random sampling? how to carry it out?
It can be carried out through a sampling frame being assigned numbers, then using a random number generator or a calculator to choose. (ran# x range of sampling frame)
What is systematic sampling?
When a sample is chosen at particular intervals from a list.
What is stratified sampling?
when the population is divided into mutually exclusive strata, and is then randomly sampled from there.
What is quota sampling?
when a researcher selects sampling units that fit the characteristics of the whole population.
What is opportunity sampling?
When the people that are available at the time of the study, and fit the criteria for it are used as a sampling frame.
What are pros and cons of random sampling?
Pros:
- Not biased
- easy and cheap for small populations
Cons:
- a sampling frame is needed
- not suitable when the population size is too large.
What are the pros and cons of systematic sampling?
Pros:
- simple and quick
- suitable for large populations
Cons:
- can introduce bias
- a sampling frame is needed
What are pros and cons of stratified sampling?
Pros:
- sample accurately represents the population.
- guarantees proportional representation of the groups within a population.
Not usable if population too large
sampling frame needed
What are the pros and cons of Quota sampling?
Pros:
- small sample can be representative of the population
- simple and easy, inexpensive
Cons:
- can introduce bias
- might have to split into more groups, which can add time and expense
- non-responses aren’t recorded
What are the pros and cons of opportunity sampling?
Pros:
- easy
- inexpensive
Cons:
- dependant on the individual researcher
- Unlikely to provide a representative sample.
What are the different types of data?
- quantitative
- qualitative
- discrete or continuous
What is continuous data?
A variable can take any value in a given range. eg: 2.5, 2.1 secs.
What is discrete data?
A variable can take only specific values in a given range. Eg: you cant really have 4.5 people in a family.
What are the places in the UK that have been mentioned in the large data set?
Heathrow
Camborne
Hurn
Leeming
Leuchars
What are the places internationally that have been mentioned in the large data set?
Jacksonville
Beijing
Perth
what are the assumptions of the particle model?
- mass concentrated at a single point
- rotational forces and air resistance can be ignored
what are some assumptions of the rod model?
mass concentrated along a line
no thickness
rigid
what are the assumptions of the lamina model?
mass distributed as a flat surface
What are some assumptions about the uniform body model?
mass concentrated at the centre of mass.
What are some assumptions of the Light object model?
objects have 0 mass
tension is the same at both ends of a light string
What are some assumptions of the inextensible string model?
acceleration is the same in objects connected by a taut inextensible string
What are some assumptions of the smooth surface model?
no friction
what are some assumptions of the rough surface model?
THere is friction present if acted on by a force
what is an assumption of a wire
treated as one dimensional
smooth and light pulley model assumptions
- pulley has no mass
- tension on both sides is the same along the sides of the beam
What are some assumptions of the bead model?
Moves freely along a wire or string
tension is the same on either side of the bead
what are some assumptions of the peg model
- dimensionless and fixed
- can be rough or smooth (question dependant)
