Chapter 1 Flashcards
What does a population consist of?
All the items we are interested in(not always people)
What is a sample?
A subset of items chosen from a population
What is each individual item in the population that can be sampled known as?
A sampling unit
What is a sampling frame?
Sampling units from a population individually framed or numbered to form a list called a sampling frame
What is the advantage of a census?
Should give a completely accurate result
3 disadvantages of a census?
-time consuming and expensive
-large volumes of data to process
-can not be used when testing involves destruction
3 advantages of a sample?
-less expensive
-less time consuming
-less data to process
3 disadvantages of a sample?
-data may not be accurate-
sample may not be large enough to represent small sub-groups of the population
Simple random sampling..
Allocate between 1 and N to each pupil
-Siena random number generator to select x different numbers, pupils corresponding to the numbers get selected
3 advantages of simple random sampling?
-bias free
-east and cheap to implement for small populations and samples
-each sampling unit has an equal chance of being selected
3 disadvantages of random sampling?
-not suitable when population size Is large
-sample may not accurately reflect the population
-sampling frame is needed
2 advantages of systematic sampling?
-simple and quick to use
-suitable for large samples and populations
2 disadvantages of systematic sampling?
-sampling frame is needed
-can introduce bias or the sampling frame is small and not random as patterns can be picked up in the data
Describe systematic sampling…
Required elements chosen at regular intervals from an ordered list
-size n is needed each item numbered randomly 1 to N
Pick every Kth element
2 advantages of stratified sampling?
-sample accurately reflects population structure
-guarantees proportional representation or groups within population
2 disadvantages of stratified sampling?
-sampling frame is needed and population must be clearly classified into distinct strata
-selection within each strata suffers from same disadvantages as simple random sampling
Describe stratified sampling?
-divide population into strata
-simple random sampling within strata
What are 2 advantages of continuous/opportunity sampling?
-easy to carry out
-inexpensive
2 disadvantages of opportunity/continuous sampling?
-unlikely to provide a representative sample
-highly dependent on individual research
What is opportunity/continuous sampling?
Sample taken from people who are available at time of study, who meet criteria
Advantages of quota sampling (3)?
-small groups are still represented in a population
-no sampling frame required
-relatively quick, inexpensive and easy
Disadvantages of quota sampling(3)
-non-random sampling can introduce bias
-can depend on knowledge/expertise of researcher
-population must be divided into groups which can be costly or inaccurate
What is quota sampling?
Population divided into groups according to characteristics
And sampling a given number of people from each group
What is qualitative data?
Non-numerical values
What is quantitative data?
Numerical values
What is continuous data?
Data that can take any decimal value
What is discrete data?
Data that can only take specific values
(E,g shoe size or number of children)
LDS: what are the international places?
-Perth Australia
-Jacksonville USA Florida
-Beijing China
Where are the 5 UK weather stations?
Heathrow London
Hurn, Dorset,south England
Camborne Cornwall SW England
Leuchars fife E Scotland
Leeming, Yorkshire North England
What does tr mean?
Les than 0.05 (use 0.025)
What is gust measured in?
Knots
Describe the Beaufort scale (kn)
0=calm (<1kn)
1-3= light (1-10kn)
4= moderate (11-16 kn)
5= fresh (17-21 kn)
What is 1kn equal to in mph?
1.15 mph
What are the 14 variables we need to know?
DM=daily mean
DT=daily total
-DM temperature
-DR rainfall
-DT sunshine
-daily maximum relative humidity
-DM visibility
-DM total cloud
-DM pressure
-daily maximum gust
-DM wind speed (kn)
-DM winspeed (Beaufort conversion)
-DM wind direction
-daily maximum gust direction
-daily maximum gust direction
What happened in October 1987
Hurricane -higher rain than may and September of that year
What happened in October 1987 and 2015 in Beijing?
Significantly colder relative to may-September
