Stats Chapter 1

Question 1

What is a population

Answer 1

The whole set of items that are of interest

Question 2

What’s a sample

Answer 2

Some subset of the population intended to represent the population

Question 3

What’s a sampling unit

Answer 3

Each individual thing in the population that can be sampled

Question 4

What’s a sampling frame

Answer 4

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

Question 5

What is a census

Answer 5

When data is collected from the entire population

Question 6

What are the advantages of a census

Answer 6

Should give a completely accurate result

Question 7

What are the disadvantages of a census

Answer 7

-time consuming and expensive
-can’t be used when testing involves destruction
-large volume of data to process

Question 8

What are the advantages of a sample

Answer 8

Cheaper
Quicker and lesss data to process

Question 9

What are the disadvantages of a sample

Answer 9

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

Question 10

Why is random sampling a good thing

Answer 10

Want each thing in sampling frame to have an equal chance of being chosen in order to avoid bias

Question 11

What is simple random sampling

Answer 11

Every sample has an equal chance of being selected

Question 12

What is the method for simple random sampling

Answer 12

In a Sampling frame each item has an identifying number and a random number generator is used

Question 13

What are the advantages of simple random sampling

Answer 13

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

Question 14

What are the disadvantages of simple random sampling

Answer 14

Not suitable when population size is large
Sampling frame is needed

Question 15

What is systematic sampling

Answer 15

Required elements are choose at regular intervals in ordered list

Question 16

What’s the method for systematic sampling

Answer 16

From a sampling frame items given identifying numbers and interval chosen. Random number hose in first interval then after that each interval item

Question 17

What are the advantages to systematic sampling

Answer 17

Simple and quick to use
Suitable for large samples/populations

Question 18

What are the disadvantages to systematic sampling

Answer 18

Sampling frame needed
Can introduce bias if sampling frame not random

Question 19

What is stratified sampling

Answer 19

Population is divided into groups (strata) and a simple random sample is carried out in each group
Used when sample is large and population naturally divides into groups

Question 20

Advantages of stratified sampling

Answer 20

• reflects population structure
  -guarantees proportional representation of groups within population

Question 21

Disadvantages of stratified sampling

Answer 21

-population must be clearly classified into distinct strata
-selection within each stratum suffers from same disadvantages as simple random sampling

Question 22

What is quota sampling

Answer 22

Population divided into groups according to characteristic. A quota of items or people in each group is set to try and reflect the groups proportion in the whole population. Interviewer selects the actual sampling units

Question 23

Advantages of quota sampling

Answer 23

• allows small sample to still be representative of whole population
  -no sampling frame required
  -quick easy and inexpensive
• allows for easy comparison between different groups in population

Question 24

Disadvantages of quota sampling

Answer 24

-Non random sampling can introduce bias
-population must be divided into groups which can be costly or inaccurate
-increasing scope of study increases number of groups adding time or expense
-non responses are not recorded

Question 25

What’s opportunity sampling

Answer 25

Sample taken from people who are available at the time and meet study criteria

Question 26

Advantages of opportunity sampling

Answer 26

-Easy to carry out
-inexpensive

Question 27

Disadvantages of opportunity sampling

Answer 27

-unlikely to provide a representative sample
-highly dependant on individual researcher