Data Collection and Interpretation

Question 1

Population?

Answer 1

• The whole set of items

Question 2

Sample?

Answer 2

• Subset of population
• Intended to represent the population

Question 3

Sampling unit?

Answer 3

• Each individual item in population

Question 4

Census?

Answer 4

• Data collected from the whole population

Question 5

Census advantages and disadvantages

Answer 5

Advantage:
* Completely accurate result

Disadvantage:
* Time consuming
* Expensive
* Cannot be used when testing involves destruction
* Large volume of data to process

Question 6

Parameters?

Answer 6

• A calculation of a sample/population

Question 7

Sampling error?

Answer 7

• The difference between the actual value of a parameter and the value derived from a sample

Question 8

What can result in a biased sample?

Answer 8

• Sample not representative of population
• Wrong person asking questions
• Small sample size

Question 9

Random vs non-random sampling?

Answer 9

• Random: every item has an equal chance of being selected for the sample
• Non-random: sample selection based on other factors

Question 10

Simple random sampling method?

Answer 10

• Each item in sampling frame has identifying number
• Use random number generator/lottery sampling

Question 11

Simple random sampling advantages/disadvantages?

Answer 11

Advantages:
* Bias free
* Easy/cheap
* Equal chance of being selected

Disadvantages:
* Not suitable for large population size
* Sampling frame needed

Question 12

Systematic sampling method?

Answer 12

• Take every kth element

k = pop size/samp size

Question 13

Systematic sampling advantages/disadvantages?

Answer 13

Advantages:
* Simple
* Suitable for large samples

Disadvantages:
* Sampling frame needed
* Can introduce bias if sampling frame is not random

Not random if there are patterns in data e.g. students are in order of ability

Question 14

Stratified sampling method?

Answer 14

• Population divided into groups (strata) and simple random sampling carried out in each group
• samp size/pop size simple randomly ampled from each strata

Question 15

Stratified sampling advantages/disadvantges?

Answer 15

Advantages:
* Reflects population structure
* Guarantees proportional representation of groups within population

Disadvantages:
* Pop must be clearly classified into distinc strata
* Same as random sampling

Question 16

Oppportunity/Convenience sampling method?

Answer 16

• Sample taken from people who are available at the time of study and meet criteria

Question 17

Opportunity/Convenience sampling advantages/disadvantages?

Answer 17

Advantages:
* Easy
* Inexpensive

Disadvantages:
* Unlikely to provide a representative sample
* Highly dependent on individual researcher

Question 18

Cluster sampling method?

Answer 18

• Define each cluster
• Collect samples from each cluster

Question 19

Cluster sampling advantages/disadvantages?

Answer 19

Advantages:
* No sampling frame
* Inexpensive

Disadvantages:
* Unlikely to provide a representative sample because clusters have similar characteristics = overrepresentation within a cluster

Question 20

Quota sampling method?

Answer 20

• Pop. divided into groups according to characteristics
• Interviewer selects the actual sampling method

Question 21

Quota sampling advantages/disadvantages?

Answer 21

Advantages:
* Allows small sample to still be representative of population
* No sampling frame needed
* Easy/inexpensive
* Allows for easy comparison between groups in population

Disadvantages:
* Non-random sampling can introduce bias
* Population has to be divided into groups (may be inaccurate)