SAMPLING Flashcards
(19 cards)
2 disadvantages of a sample
- Data not be completly accurate
- Sample not large enough to give information ab small subgroup of population
2 advantages of sampling
- Less time consuming and expensive than a cenus
- Less data to process
1 advantage of cenus
Should be completly accurate
3 disadvanatges of Cenus
1.Time consuming and expensive
2. Hard to process as large quantity of data
3. Cant be usend when testing process destroyes the item
Method for simple random sampling
Number all items in the population
Use random number generator
Select item corresponding to these numbers
Method for systematic sampling
Allocate a number to all items in the population
Let n = population size/sample size
Use randome number generator from 1 to n to select the first item
Vhoose every nth ithem after that
Method stratified samplimg
Allocate a number from 1 to n in each group
N = Number in group x sample size / number in population
Use random number generator to select items from each group
Select item from each group corresponding to these numbers
Disadvantage of opportunity sampling
Difficult to get a list of all people
Quota sampling method
Population divided into groups
N= number in group x sample size / number in population
Collect data from the first n people
Opportunity sampling advantages 3
Cheap
Easy to carry out
No sampling frame needed
Opportunity sampling disadvantages
Unlikely to provide a representative sample
Wuota sampling advantages 3
No sampling frame needed
Quick , easy and cheap
Representation of population
Quota sampling disadvanatges 3
Can have bias
Population must be divided into groups
Advantages of stratified sampling 2
Sample accuratky reflects population
Garanties proportion representation if groups within population
Stratified sampling disadvantages 2
Population must be classified into groups
Selection for each group suffers from some disadvantages as sample random sampling
Systematic sampling advantages 2
Simple and quick
Suitable vor large population snd large samples
Systematic sampling disadvanatges 2
Sampling frame is needed
Can have hias if sampling frame not random
Simple random sampling advantages 3
Free from bias
Easy and cheap
Each sampling unit has an equal chance of being selected
Simple random sampling disadvantages 3
Not suitable when population size or sample size is very large
Sampling frame is needed
