Ch1: data collection

Created by

Connor Bannon

Cards (40)

Advantages of a census
Should give a completely accurate result
disadvantages of a census
time consuming and expensive
cant be used when the testing destroys the item
hard to process large quantities of data
advantages of a sample 
less time consuming and expensive than a cencus
fewer people have to respond
less data to process than in a cencus
disadvantages of a sample
the data may not be as accurate
the sample may not be large enough to give information about small subgroups of the population
individuals of a population are known as…
sampling units
what is a sampling frame?
when sampling units of a population are individually named or numbered to form a list
In random sampling, every member of the population has an equal chance of being selected. this helps with…
the sample being representative of the population
helps remove bias
What are the three methods of random sampling?
simple random sampling
systematic sampling
stratified sampling
A random sample of size n is one where every sample of size n has…
an equal chance of being selected
How do you carry our a simple random sample?
you need a sample frame, allocate each sampling unit a unique number and a selection of these numbers are chosen at random.
choose the numbers via random number generator or lottery sampling
what is lottery sampling?
the member of the sampling frame can be written on tickets and placed into a hat and picked out
what is systematic sampling?
the required elements are chosen at regular intervals from an ordered list (e.g every fifth person is chosen). the first person should be chosen at random
what is stratified sampling?
the population is divided into mutually exclusive strata (male and female for example) and a random sample is taken from each. the proportion of each strata sampled should be the same.
how do you find the number sampled in a stratum?
(number in stratum/ number in population) x overall sample size
advantages of simple random sampling
free of bias
easy and cheap to implement for small populations and samples
each sampling unit has a known and equal chance of selection
disadvantages of simple random sampling
not suitable when the population size or the sample size is large
a sampling frame is needed
advantages of systematic sampling
simple and quick
suitable for large samples and large populations
disadvantages of systematic sampling
a sampling frame is needed
it can introduce bias if the sampling frame isn’t random
advantages of stratified sampling
sample accurately reflects the population
guarantees proportional representation of groups within a population
disadvantages of stratified sampling
population must be clearly classified into distinct strata
selection within each stratum suffers from the same disadvantages as simple random sampling
What are the two types of non random sampling
Quota sampling
Opportunity sampling
what is quota sampling?
When an interviewer or researcher selects a sample that reflects the characteristics of the whole population
What is opportunity sampling?
Consists of taking the sample reom people who are available at the time the study is carried out and who fit the criteria you’re looking for
Quota sampling advantages  
Allows a small sample to still be representative of the population
No sampling frame required
Quick, easy and inexpensive
Allows for easy comparison between different groups within a population
quota sampling disadvantages
non random sampling introduces bias
population must be divided into groups which can be costly or inaccurate
increasing scope of study increases number of groups adding to time and expense
non responses are not recorded as such
opportunity sampling advantages
easy to carry out
inexpensive
opportunity sampling disadvantages
unlikely to provide a representative sample
highly dependent on individual researcher
What are quantitative variables/data?
Includes numerical observations
what are qualitative variables/data?
includes non numerical observations
what is a continuous variable?
A variable that can take on any value within a certain range.
what is a discrete variable?
A variable that can only take on specific, distinct values.
when data is presented in a grouped frequency table, the specific data values are not shown. The groups are more commonly known as classes. What is true about these?
Class boundaries tell you the max and min values that belong in each class
the midpoint is the average of the class boundaries
the class width is the difference between the upper and lower class boundaries
In the large data set, what cities are used?
Leuchars
Leeming
Heathrow
Hurn
Camborne
Jacksonville
Beijing
Perth
Where is Leuchars?
Scotland
Where is Leeming?
North Yorkshire
Where is Hurn? 
In the far south centre of the UK
Where is Camborne? 
Cornwall
What stats are shown on the large data set?
Daily mean temperature (in C)
Daily total rainfall (<0.05mm recorded as tr or trace)
Daily total sunshine (nearest 10th of an hour)
Daily mean wind direction and wind speed in knots (1kn=1.15mph) on the Beaufort scale
Daily max gust
Daily max relative humidity
What does the Beaufort scale show?
0 is calm and <1 knot avg speed 10m above ground
1-3 is light and 1-10 knots avg speed 10m above the ground
4 is moderate and 11-16 knots avg speed 10m above the ground
5 is fresh and 17-21 knots avg speed 10m above the ground
What is shown on the large data set (2)
daily mean cloud cover (in oktas or eights of the sky covered by clouds)
Daily mean visibility (in decametres)
Daily mean pressure (in hectopascals (hPa))