Sampling methods

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 whole population

Question 3

sampling unit

Answer 3

each individual thing in the population that can be sampled

Question 4

sampling frame

Answer 4

sampling units of a population which are individually named or numbered to form a list

Question 5

census

Answer 5

data collected from the entire population

Question 6

adv of census

Answer 6

should give completely accurate result

Question 7

adv of sample

Answer 7

cheaper
quicker
less data to process

Question 8

disadv of census

Answer 8

time consuming
expensive
cannot be used when testing involves destruction
large volume of data to process

Question 9

disadv of sample

Answer 9

data may not be accurate
data may not be large enough to represent small sub-groups

Question 10

what is simple random sampling

Answer 10

when every sample has an equal chance of being selected

Question 11

method for simple random sampling

Answer 11

in the sampling frame, each item has an identifying number. a random number generator is used.

Question 12

adv of simple random sampling

Answer 12

bias free
easy and cheap to implement
each number has a known equal chance of being selected

Question 13

disadv of simple random sampling

Answer 13

not suitable when population size is big
sampling frame needed

Question 14

methods for selecting a random number

Answer 14

calc
computer
rando number tables

Question 15

how to use calc for simple random samp

Answer 15

use RAN# and multiply given number by population size.
ignore the decimal

Question 16

what is systematic sampling

Answer 16

required elements are chosen at regular intervals in a ordered list

Question 17

formula for systematic sampling

Answer 17

pop size / samp size = K
start at a random item between 1 and K

Question 18

adv of systematic sampling

Answer 18

simple
quick to use
suitable for large populations/samples

Question 19

disadv of systematic sampling

Answer 19

sampling frame again needed
can introduce bias if sampling frame not needed

Question 20

what is stratified sampling

Answer 20

population divided in groups(strata) and a simple random sample carried out in each group

samp/pop size sampled from each strata

Question 21

when is stratified sampling used

Answer 21

when sample is large and population naturally divides into groups

Question 22

adv of stratified samp

Answer 22

reflects population structure
guarantees proportional representation of groups within population

Question 23

disadv of stratified samp

Answer 23

population must be clearly classified into distinct data

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

Question 24

Quota sampling

Answer 24

The population is divided into groups (gender,age, etc)
A given number (quota) is surveyed in each group
This type of sampling is not random and is used in market research

Question 25

Adv of quota

Answer 25

Cheap
Easy and quick to carry out

Question 26

Convenience sampling

Answer 26

Choosing a sample that is given/seen first. For an example, a sample of 60 could be the first 60 people in a lecture to attend.

Question 27

Adv of convenience

Answer 27

Quick/time efficient
Instant results

Question 28

Disadvantage of convenience

Answer 28

Highly likely to be biased and unrepresentative
Can lead to errors
Unreliable