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

Sampling unit

Answer 3

Each individual thing in that population

Question 4

Sampling frame

Answer 4

List of sampling units

Question 5

Census

Answer 5

Data collected from the entire population

Question 6

Census advantages

Answer 6

Should give completely accurate result

Question 7

Census disadvantages

Answer 7

• time consuming +expensive
• can’t be used when testing involves destruction
• large data of volumes to process

Question 8

Sample advantages

Answer 8

Cheaper
Quicker
Less data to process

Question 9

Sample disadvantages

Answer 9

Data may not be accurate

Data may not be large enough to represent small sub-groups

Question 10

Random sampling

Answer 10

Gives everything an equal chance of being chosen to avoid bias

Question 11

Simple random sampling method

Answer 11

In the sampling frame each item is assigned a number

Use a random number generator or ‘lottery sampling’ (names in hat)

Question 12

Simple random sampling advantages

Answer 12

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

Question 13

Simple random sampling disadvantages

Answer 13

Not suitable when pop is lrg
Sampling frame needed
Can introduce bias if sampling from =not random

Question 14

Systematic sampling+method

Answer 14

Required elements r chosen at regular intervals in ordered list
E.g. take every Kth element where
K=pop size(n) /sample size (n)
Start at random item between 1 and k

Question 15

Systematic sampling advantages

Answer 15

Simple +easy to use

Suitable for lrg samples

Question 16

Systematic sampling disadvantages

Answer 16

Sampling frame again needed

Can introduce bias if sampling frame not random

Question 17

Stratified sampling +method

Answer 17

Population divided into groups (strata) and a simple random sample carried out in each group (same proportion )
Sample size (n)/population (N) sampled from each strata
Used when lrg+ pop naturally divides into groups

Question 18

Advantage of stratified sampling

Answer 18

Reflects population structure

Guarantees proportional representation of groups within population

Question 19

Disadvantages of stratified sampling

Answer 19

Population must be clearly classified into distinct strata

Selection within each stratum suffers from same disadvantages as simple random sampling

Question 20

Quota sampling +method

Answer 20

Pop divided into groups according to characteristic
a quota of items/ppl in each group is set to try nd reflect group’s proportion in whole pop
Interviewer selects actual sampling units

Question 21

Quota sampling advantages

Answer 21

Allows small sample still representative of pop
No sampling frame required
Relatively easy+ inexpensive
Allows for easy comparison between different groups in pop

Question 22

Quota sampling disadvantages

Answer 22

Non- random sampling can intro bias
Pop must be divided into groups -can be costly/inaccurate
Increasing scope of study increases no. groups adding
Non-responses= not recorded

Question 23

Opportunity/ convenience sampling

Answer 23

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

Question 24

Advantage opportunity sampling

Answer 24

Easy to carry out

Inexpensive

Question 25

Disadvantages opportunity sampling

Answer 25

Unlikely to provide a representative sample

Highly dependent on individual researcher