Chapeter 1

Question 1

What is a population?

Answer 1

Consists of all the items we are interested in

Question 2

What is a sample?

Answer 2

A subset of items chosen from the population

Question 3

What is a sampling frame?

Answer 3

Sampling unites of a population that are individually named or numbered to form a list of

Question 4

Advantages of a census?

Answer 4

Should give completely accurate results

Question 5

Advantages of a sample?

Answer 5

Less expensive
Less time consuming
Less data to process

Question 6

Disadvantages of a census?

Answer 6

Time consuming and expensive
Can not be used when testing involves destruction
Large volume of data to process

Question 7

Disadvantages of a census?

Answer 7

Data may not be accurate
Sample may not be large enough to represent small sub-groups of the population

Question 8

What is a census?

Answer 8

Observes or measures every member of a population

Question 9

What is simple random sampling?

Answer 9

Where every sample of size n has an equal chance of being selected

Question 10

What is systematic sampling?

Answer 10

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

Question 11

What is stratified sampling?

Answer 11

The population is divided into mutually exclusive strata (males, and females, for example) and a random sample is taken from each

Question 12

Advantages of simple random sampling?

Answer 12

• Free of bias
• Easy and cheap
• Each sampling unit has an equal chance of getting selected

Question 13

Disadvantages of simple random sampling?

Answer 13

• Not suitable when population size is large
• A sampling frame is needed

Question 14

Advantages of systematic sampling?

Answer 14

• Quick to use
• Suitable for large samples

Question 15

Disadvantages of a systematic sampling frame?

Answer 15

• A sampling frame I needed
• Can introduce bias

Question 16

Advantages of stratified sampling?

Answer 16

• Sample reflects population structure
• Guarantees proportional representation

Question 17

Disadvantages of stratified sampling?

Answer 17

• Population must be clearly classified into distinct strata
• Selection suffers from simple random sampling

Question 18

What is quota sampling?

Answer 18

An interviewer or researcher selects a sample that reflects the characteristics of the population

Question 19

What is opportunity sampling?

Answer 19

Consists of taking the sample from people who are available at the time of the study and who fit the criteria

Question 20

Advantages of quota sampling?

Answer 20

• Allows a small sample to still be representative of the population
• No sampling frame required
• Quick, easy and inexpensive

Question 21

Disadvantages of quota sampling?

Answer 21

• Non-random sampling can introduce bias
• Population must be divided into groups, which can be costly or inaccurate

Question 22

Advantages of opportunity sampling?

Answer 22

• Easy o carry out
• Inexpensive

Question 23

Disadvantages of opportunity sampling?

Answer 23

• Unlikely to provide a representative sample
• Highly dependent of individual researcher

Question 24

What is quantitative variables?

Answer 24

Numerical observations

Example: Shoe size

Question 25

What is qualitative variables?

Answer 25

Non-numerical observations Example: hair colour (red, blonde, brunette)

Question 26

What is continuous data?

Answer 26

Can take any value e.g. can go into decimals

Question 27

What is discrete data?

Answer 27

Can take only specific values e.g. whole numbers

Question 28

Daily mean temperature?

Answer 28

The average hourly temperature readings during a 24-hour period

Question 29

Daily total rainfall?

Answer 29

Including solid precipitation such as snow and hail, which is melted before being included Amounts less than 0.05mm are recorded as Tr

Question 30

Daily total sunshine?

Answer 30

Recorded to the nearest tenth of an hour

Question 31

Daily mean wind direction and wind speed?

Answer 31

In knots, averages over 24 hours from midnight to midnight. Mean wind directions are given as bearings. Categorised according to the Beaufort scale.

Question 32

Daily maximum gust?

Answer 32

In knots - this is the highest instantaneous wind speed recorded. The direction from which the maximum gust was blowing is also recorded

Question 33

Daily maximum relative humidity?

Answer 33

Given as a percentage of air saturation with water vapour. Relative humidities above 95% give rise to misty and foggy conditions

Question 34

Daily mean cloud cover?

Answer 34

Measured in okras or eighths of the sky covered by clouds

Question 35

Daily mean visibility?

Answer 35

Measured in December res. This is the greatest horizontal distance at which an object can be seen in daylight

Question 36

Daily mean pressure?

Answer 36

Measured in hectopascals (ha)