Data collection Flashcards
Qualitative
Data that usually given in words not numbers to describe something
Quantitative
Data that is given using numbers which counts or measures something
Discrete
A variable that can take only specific values in a given range
Continuous
A variable that can take any value in a given range
class boundaries
They tell the maximum and minimum values that belong in each class
midpoint
the average of the class boundaries
class width
the difference between the upper and lower class boundaries
population
A whole set of the things that you are interested in
sample
A subset of the population which is used to collect the data from
sampling frame
a list of all members of the population
sample unit is one thing within sampling frame
population parameter
a numerical value which describes a characteristic of the population
sample statistic
a value computed using data from the sample
Census Definition
Collects data about all the members of a population
Census Adv
Gives fully accurate results
Census Disadv
Time consuming and expensive to carry out, can destroy or use up all the members of a population when they are consumable
Sampling Def
collects data from a subset of the population, the size of sample can affect the validity of any conclusion drawn
Sampling Adv
quicker and cheaper, less data needed to be analysed
Sampling DisAdv
might not represent the population accurately, could introduce bias
Simple Random Def
A sample where every possible sample of size n has an equal chance of being selected
Simple Random Adv
Easy for small samples
Random Sample
Free of bias
Simple Random DisAdv
Difficult for large samples
Sampling frame
Systematic Sampling Def
Where every nth person is picked from an ordered sampling frame
Systematic Sampling Adv
Random Sample
Quick / Easy for small samples
Systematic Sampling DisAdv
Sampling frame needed
If list is not random, the sample may not b random
Stratified Sampling Def
The population is divided into disjoint groups(called strata) and then a random sample is taken form each group(stratum)
- The proportion of a stratum that is sampled is equal to the proportion of the population that belong to that stratum
Stratified sampling Adv
Sample accurately reflects the population structure, Guarantee proportional representation of groups within a population
Stratified Sampling DisAdv
Population must be clearly classified into distinct strata, selection within each stratum suffers from the same disadvantages as simple sampling
Quota Sample Def
Where the population is split into strata (groups) and a sample size is chosen for each group that is
proportional to the group size. These people are then selected on a first come first served basis. Once you reach your
quota, you stop.
Opportunity sampling
consists of taking the sample from people who are available at the time the study is carried out and who fit the criteria you are looking for
Opportunity Sampling Adv
Easy to carry put, Inexpensive
Quota Sample Adv
Do not need sampling frame
Quick easy + cheap
Reflects population
Structure
Opportunity sampling Disadv
Quota Sample DisAdv
Not random sample
People may refuse
Interviewer bias
Not always possible to split population into distinct groups
