Chapter 1 - Data Collection

Question 1

What is a Population?

Answer 1

A Population is the whole set of people or items that are of interest

Question 2

What is a Census?

Answer 2

It observes or measures every member of a population

Question 3

What is a sample?

Answer 3

Its a selection of observations taken from a subset of the population to find out info about a population as a whole

Question 4

What are the advantages and disadvantages of using a census?

Answer 4

Advantage:
It should give a completely accurate result

Disadvantages:

• Time Consuming
• Expensive
• cant be used if the testing process destroys the item
• Hard to process large quantity of data

Question 5

What are the advantages and disadvantages of using a sample?

Answer 5

Advantages:

• Less Time Consuming than a census
• less expensive than a census
• Fewer people have to respond
• Less data to process compared to a census

Disadvantages:

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

Question 6

What are sampling units?

Answer 6

They’re individual units of the population e.g -> Someones name in a register

Question 7

What is a sampling frame?

Answer 7

Its a list of sampling units which have been numbered or named individually e.g a register or list

Question 8

What is Simple Random Sampling?

Answer 8

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

Question 9

How is Simple Random Sampling Carried out?

Answer 9

1. A Sampling Frame is needed
2. Each person is given a unique number (the selection of these numbers are chosen at random)
3. Numbers are chosen using a (Random Number generator, computer, calculator etc) or a LOTTERY SAMPLE

To do the LOTTERY SAMPLE method numbers should be placed into a ‘hat’ and then the required amount of numbers should be pulled out.

Question 10

What is Systematic Sampling?

Answer 10

The required number of elements are chosen at regular intervals from an ordered list e.g. Every 5th person

(the first sample should be chosen at random)

Question 11

What is Stratified Sampling?

Answer 11

A sampling method that involves the population to be divided into mutually exclusive strata (e.g. females and males) and a random sample is taken from each

Question 12

What is the formula for stratified sampling?

Answer 12

The number of sample in a strata

number in strata/ number in population

(answer) x overall sample size

Question 13

What are the advantages and disadvantages of using a Simple Random Sampling?

Answer 13

Advantages:

• Free of bias
• Easy and cheap to implement for small populations and small samples
• Each sampling unit has a known and equal chance of selection

Disadvantages:

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

Question 14

What are the advantages and disadvantages of using a Systematic Sampling ?

Answer 14

Advantages:

• Simple and quick to use
• suitable for large samples and populations

Disadvantages:

• A sampling frame is needed
• it can introduce bias if the sampling frame is not at random

Question 15

What are the advantages and disadvantages of using a Stratified sampling?

Answer 15

Advantages:

• The sample accurately reflects the population structure
• Guarantees proportional representation of groups within a population

Disadvantages:

• The population must be clearly classified into distinct strata
• Not suitable when the population size or sample size is large
• A sampling frame is needed

Question 16

What are the types of Non-Random Sampling?

Answer 16

Quota and Opportunity Sampling

Question 17

What is quota Sampling?

Answer 17

its when an interviewer or researcher selects a sample that reflects the characteristics of the whole population

Question 18

What is Opportunity Sampling?

Answer 18

it consists of taking the sample from people who are available at the time the study is carried out and who fit the criteria you are looking.

e.g first 20 people you meet outside a super market

Question 19

How is quota sampling carried out?

Answer 19

1. The pop is divided into groups to a given characteristic
2. The interviewer will meet people, assess their groups and then, after interview, allocate them into the appropriate quota.
3. This continues until all quotas have been filled, if someone refuses or the quota into which they fit into is full then theyre just ignored and the next person is interviewed

Question 20

What are the advantages and disadvantages of using Quota sampling?

Answer 20

Advantages:

• Allows a small sample to still be representative of the population
• No sampling frame required
• Quick and easy and inexpensive
• allows for easy comparison between dfferent groups within a population

Disadvantages:

• 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, which adds time and expense
• Non-response are not recorded as such

Question 21

What are the advantages and disadvantages of using an opportunity sampling?

Answer 21

Advantages;

• easy to carry out
• inexpensive

Disadvantages:

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

Question 22

How many types of random sampling are there?

Answer 22

There are 3 types:
Simple random sampling
stratified sampling
systematic sampling

Question 23

What are QuanTitative Variables/ Data?

Answer 23

They’re variables or data associated with numerical observations

e.g. shoe size

Question 24

What are QuaLitative Variables/ Data?

Answer 24

They’re variables or data not associated with numerical observations

e.g. Hair colour

Question 25

What are continuous variables?

Answer 25

They’re variables that can take any value in a given range

e.g. Time, Distance (2 secs, 2.1 secs 2.01 secs etc..)

Question 26

What are discrete variables?

Answer 26

They’re variables that can take only specific values in a given range

e.g. The number of girls in a family (you cant have 2.65 girls in a family )

Question 27

What does the class boundary tell you?

Answer 27

It tells you the maximum and minimum values that belong to each class

Question 28

What is the midpoint ?

Answer 28

Its the average of the class boundaries

Question 29

What is the class width?

Answer 29

Its the difference between the upper and lower class boundaries