Chapter 1 stats

Question 1

Population

Answer 1

The whole set of items that are of interest

Question 2

Sample

Answer 2

some subset of the population intended to represent the population

Question 3

Parameter

Answer 3

A number which describes the entire population. Tends to be the thing we are measuring.

Question 4

Statistic

Answer 4

A number taken from a single sample - can use 1 or more to estimate the parameter, larger sample - more reliable the parameter.

Question 5

Census

Answer 5

Data collected from the entire population.

Question 6

Sampling unit

Answer 6

Each individual thing in the population that can be sampled.

Question 7

Sampling frame

Answer 7

A list of named or numbered sampling units of a population.

Question 8

Census
Advantages / Disadvantages

Answer 8

Adv:
Should give completely accurate result
Disadv:
Time consuming + expensive
Can’t be used when testing involves destruction
Large vol of data to process

Question 9

Sampling
Advantages / Disadvantages

Answer 9

Adv:
Cheaper
Quicker
Less data to process
Disadv:
Data may not be accurate
Data may not be large enough to represent small sub-groups

Question 10

When is a sampling method biased?

Answer 10

If it creates a sample which doesn’t represent the population.

Question 11

Simple random sampling:
What is it?

Answer 11

Every sampling unit in the sampling frame has an equal chance of being selected.

Question 12

Simple random sampling:
How to carry out?

Answer 12

• Allocate a number to each item
• Use a random number generator to pick out __ different numbers
• The corresponding items form the sample

Question 13

Simple random sampling:
Advantages

Answer 13

Bias free
Easy + cheap to implement
Each number has a known equal chance of being selected

Question 14

Simple random sampling:
Disadvantages

Answer 14

Not suitable when sampling frame is large
Sampling frame needed

Question 15

Systematic sampling:
What is it?

Answer 15

Required elements are chosen at regular intervals in ordered list

Question 16

Systematic sampling:
How to carry out?

Answer 16

Take every ‘k’th element where K = pop size / sample size stanting at random items between 1 and K

Question 17

Systematic sampling:
Advantages

Answer 17

Simple + quick to use
Suitable for large samples / populations

Question 18

Systematic sampling:
Disadvantages

Answer 18

Sampling frame needed
Can introduce bias if sampling frame not random

Question 19

Stratified sampling:
What is it?

Answer 19

Population divided into groups (strata) and a simple random sample carried out in each groups

Question 20

Systematic sampling:
How to carry out?

Answer 20

Same proportion samp size / pop size sampled from each strata

Question 21

Systematic sampling:
Advantages

Answer 21

Reflects population structure
Guarantees proportional representation of groups within population

Question 22

Systematic sampling:
Disadvantages

Answer 22

Pop must be clearly classified into distinct strata
Selection within each stratum suffers from same disadvantages as simple random sampling

Question 23

Quota sampling:
How to carry out?

Answer 23

Pop divided into groups according to characteristic. A quota of items / people om each group is set to try + reflect group’s proportion in whole population. Interviewer selects the actual sampling units.

Question 24

Quota sampling:
Advantages

Answer 24

Allows small sample to still be representative of population
No sampling frame required
Quick, easy, inexpensive
Allows for easy comparison btwn diff groups in population

Question 25

Quota sampling: Disadvantages

Answer 25

Non-random sampling can introduce bias Pop must be divided into groups - can be costly or inaccurate Increasing scope of study increases number of groups - adds time + expense Non-responses not recorded

Question 26

Quota

Answer 26

A fixed share / number of something

Question 27

Opportunity / convenience sampling: How to carry out?

Answer 27

Sample taken from people who are available at time of study, who meet criteria

Question 28

Opportunity / convenience sampling: Advantages

Answer 28

Easy to carry out Inexpensive

Question 29

Opportunity / convenience sampling: Disadvantages

Answer 29

Unlikely to provide a representative sample Highly dependent on individual researcher