chapter 1 year 1 stats Flashcards
what is population
- set of items that are of interest
what is a census
- measures/observes every member of a population (data collected from entire population)
advantages of census
- accurate result
disadvantages of census
- expensive
- time consuming (hard to process large quantity of data)
- testing may destroy items
what is a sampling unit
- each individual thing that can be sampled in a population
what is a sampling frame
- sampling units of a population are individually named/numbered to form list (sampling frame)
what is a sample
- some subset of the population intended to estimate info about/represent population as a whole
generally the larger the sample…
- the more accurate it is
advantages of sample
- cheaper
- quicker
- less time to process
disadvantages of sample
- data less accurate
- sample may not be large enough to give info about sub groups of population
what is simple random sampling
- each sampling unit in sampling frame has equal chance of being selected.
how is simple random sampling carried out
- selecting members involved assigning numbers to all of them and either generating numbers at random to choose or use lottery sampling
what is lottery sampling
- members of a sampling frame are written on card and put in a hat to generate members picked
advantages of simple random sampling
- bias free
- easy and cheap to implement
disadvantages of simple random sampling
- require a sampling frame
- not suitable for large population or sample size
what is systematic sampling
- members are chosen at regular intervals from an ordered list (periodic nature)
- you take every k ᵗʰ unit, k = pop/sam
how do you start systematic sampling
- pick a random number between 1 and k for start point
advantages of systematic sampling
- simple + quick to use
- suitable for large samples and populations
disadvantages of systematic sampling
- requires sampling frame
- possible bias as units don’t have equal chance of selection if sampling frame not random
what is stratified sampling
- population divided into groups (mutually exclusive strata) and a simple random sample is taken from each.
what does a sample represent in stratified sampling
group/strata of a population
how to do stratified sampling (work out number sampled in a stratum)
number in stratum/population x overall sample size
within this pick randomly
advantages of stratified sampling
- sample accurately reflects population
- guarantees proportional representation of groups
disadvantages of stratified sampling
- population must be classified in stratas (can be time consuming)
- selection within a group has same issues as simple random sampling
give the 2 methods of non random sampling
- quota sampling
- opportunity sampling
what is quota sampling.
- an interviewer/researcher selects a sample that reflects characteristics of group/whole population as quota of items/people in each group is set
how can we carry out quota sampling
- Divide population into groups according to given characteristics.
- The size of each group
determines the proportion of the sample that should have that characteristic. - The interviewer
should assess which group people fall into, as part of the interview. Once a quota has been filled,
no more people in that group are interviewed.
what is quota sampling similar to. why are they different though
- stratified sampling
- quota sampling doesn’t have random sampling aspect and instead interviewer selects the actual sampling units by actively choosing people within group via suitable means (e.g. advertising) until quota for each group is filled
what does the word quota mean
- a fixed share/number of something
advantages of quota sampling
- quick, easy and inexpensive
-allows small sample to represent population - no sampling frame required
- allows for easy comparison between different groups within a population
disadvantage of quota sampling
- non random sampling can introduce bias
- population must be divided into groups (costly/inaccurate)
- increasing scope of study increases number of groups (adds time and expense)
- non-responses are not recorded (not willing to take part)
what is opportunity sampling
- sample is taken from people available at the time and who fit the criteria needed
what is opportunity sampling also known as
- convenience sampling
how can we carry out opportunity sampling
- interviewer selects actual sampling units according to set criteria
- they only sample people who are available at the time the study is carried out
advantages of opportunity sampling
- easy/cheap
disadvantages of opportunity sampling
- unlikely to provide representative sample (unlikely to reflect the characteristics of the whole population)
- highly dependent on individual researcher
what is qualitative data
- non numerical data
what is quantitative data
- numerical data which is either discrete or continuous
what is discrete data
- specific values in a given range
what is continuous data
- any value in a given range
when data is presented in a group frequency table, what are the groups called
- classes
what are class boundaries
- maximum and minimum values that belong in each class
what is the midpoint in grouped frequency table
- average of class boundaries
what is the class width
- difference between the upper and lower class boundaries
what 5 UK locations are included in data set
- Camborne
- Heathrow
- Hurn
- Leeming
- Leuchars
where is camborne
- cornwall
what do i have to know about heathrow
- 2nd busiest airport in the world
where is hurn
- south coast of england
where is leeming
- location of RAF base in Yorkshire
where is leuchars
- scotland
where is beijing
- capital of china
where is Jacksonville
- Florida USA
where is perth
- Australia
what 3 overseas locations are included in data set
- Beijing
- Jacksonville
- Perth
how many weather conditions do you need to know
- 11
what month period do i have to know
- 6 month period between May to Oct
what 2 years do i have to know
- 2015 and 1987
why is 1987 important
year of the great storm 15th/16th october
what are 11 weather conditions
- temperature
- rainfall
- sunshine
- windspeed
- gust
- humidity
- cloud
- visibility
- pressure
- wind direction
- gust direction
ADD TO THIS (WHAT IS EACH ONE AND MEASUREMENT)
