S3 Ch2

Question 1

Advantages of a census?(1)

Answer 1

It should give a completely accurate result

Question 2

Disadvantages of a census?(3)

Answer 2

• time consuming and expensive
• cannot be used when the testing process is to destruction
• info is difficult to process because there is so much of it

Question 3

Advantages of sample survey?(4)

Answer 3

• cost is low
• results are obtained quickly
• less people have to respond
• less data to deal with

Question 4

Disadvantages of sample survey?(2)

Answer 4

• data not as accurate as a census

- sample may not be large enough to give info about small sub groups of population

Question 5

What is a simple random sample?

Answer 5

Equal chance of being selected, set size of sample.

Question 6

Sampling frame?

Answer 6

List identifying every single sampling unit that could be included in the sample

Question 7

When is systematic sampling used?

Answer 7

When the population is too large for simple random number sampling.

Question 8

Advantages of systematic sampling?(2)

Answer 8

Simple

Suitable for large samples

Question 9

Define census?

Answer 9

A census observes or measures every member of a population

Question 10

Define population?

Answer 10

A whole set of items that are of interest

Question 11

Advantages of random number sampling? (3) and a disadvantage? (1)

Answer 11

• easy to use
• each number has a known equal chance of selection
• the numbers are truly random and free from bias
• not suitable where the population size is large

Question 12

3 advantages and 2 disadvantages of lottery sampling?

Answer 12

• tickets drawn at random
• easy to use
• each ticket has a known chance of selection
• not suitable for large population
• sampling frame is needed

Question 13

What is lottery sampling?

Answer 13

Each member can be identified by a name or number and this is put on a ticket

Tickets (all same size and shape) are put into a container and drawn one at a time without replacement

Question 14

Learn random number sampling

Answer 14

Now

Question 15

What is systematic sampling?

Answer 15

The required elements are chosen at regular intervals from an ordered list

Question 16

Systematic sampling interval equation?

Answer 16

K = (population size)/(sample size)

Question 17

Advantages of systematic sampling? (2)

Answer 17

• simple to use

- suitable for large samples

Question 18

Disadvantages of systematic sampling? (2)

Answer 18

• only random if ordered list is truly random

- can introduce bias

Question 19

What is stratified sampling?

Answer 19

• population is divided into mutually exclusive strata and a random sample is taken from each

Question 20

Advantages of stratified sampling? (2)

Answer 20

• reflects population structure

- can give more accurate estimates than simple random sampling where there are clear strata present

Question 21

When is stratified sampling used?

Answer 21

Sample is large

Population divides naturally into mutually exclusive groups

Question 22

Disadvantages of stratified sampling? (2)

Answer 22

• within strata problems are the same as for any simple random sample
• if strata are not clearly defined they may overlap

Question 23

When is systematic sampling used?

Answer 23

When the population is too large for simple random number sampling

Question 24

What is quota sampling?

Answer 24

Population divided into groups in terms of gender, age etc.

Number of people in each group I set to try and reflect the groups proportion in the whole population

Interview selects sampling units

Question 25

Advantages of quota sampling? (3)

Answer 25

• enables fieldwork to be done quickly because a representative sample can be achieved with a small sample size
• costs are low
• easy to do

Question 26

Disadvantages of quota sampling? (2)

Answer 26

• interviewer bias in who is included

- not possible to estimate the sampling errors (process not random)

Question 27

What is primary data?

Answer 27

Data that is collected by the person who is going to use the data

Question 28

What is secondary data?

Answer 28

Data that is neither collected by, nor on behalf of, the person who to use the data

Question 29

Advantages of primary data? (3)

Answer 29

Collection method is known
Accuracy is known
Exact data needed are collected

Question 30

Disadvantage of primary data? (1)

Answer 30

Costly in time and effort

Question 31

Advantages of secondary data? (3)

Answer 31

Cheap to obtain
Large quantity of data is available (eg. Internet)
Much of the data has been collected for years and can be used to plot trends

Question 32

Disadvantages of secondary data? (2)

Answer 32

Bias not always recognised

Can be in a form that is difficult to deal with

Question 33

What is a sample?

Answer 33

A selection of observations taken from a sub set of a the population.