Statistics 1: 1 Data Collection

Question 1

Population

Answer 1

The whole set of items that are of interest

Question 2

Census

Answer 2

Observes or measures every member of a population

Question 3

Sample

Answer 3

A selection of observations taken from a subset of the population which is used to find out information about the population as a whole

Question 4

Census: Advantages

Answer 4

• Should give a completely accurate result

Question 5

Census: Disadvantages

Answer 5

• Time consuming + expensive
• Cannot be used when the testing process destroys the item
• Hard to process large quantity of data

Question 6

Sample: Advantages

Answer 6

• Less time consuming and expensive than a census
• Fewer people have to respond
• Less data to process than in a census

Question 7

Sample: Disadvantages

Answer 7

• The data may not be as accurate
• The sample may not be large enough to give information about small sub-groups of the population

Question 8

Sampling units

Answer 8

individual units of a population

Question 9

Sampling frame

Answer 9

When sampling units of a population are individually named/numbered to form a list

Question 10

What should a sample be?

Answer 10

Representative of the population

Question 11

Importance of sampling being random

Answer 11

Removes bias

Question 12

3 methods of random sampling

Answer 12

• Simple random sampling
• Systematic sampling
• Stratified sampling

Question 13

Sample random sample of size n

Answer 13

Sample where every sample of size n has an equal chance of being selected

Question 14

2 methods of choosing numbers

Answer 14

• Generating random numbers (using calculator or computer)
• Lottery sampling

Question 15

Lottery sampling

Answer 15

The members of the sampling frame could be written on tickets and placed into a ‘hat’

The required number of tickers would then be drawn out

Question 16

Systematic sampling

Answer 16

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

e.g. to take a sample of 20 from a population of 100, you take every 5th person

Question 17

Stratified sampling

Answer 17

The population is divided into mutually exclusive strata (e.g. males and females) and a random sample is taken from each

• The proportion of each strata sampled should be the same