Data Handling

Question 1

What are the Random Sampling Methods?

Answer 1

Random, Systematic, Stratified

Question 2

What are the Non-Random Sampling Methods?

Answer 2

Opportunity (Convenience), Quota

Question 3

What is Random Sampling?

Answer 3

Data is picked at random, usually using some random generator

Question 4

What is Systematic Sampling?

Answer 4

Data is chosen at regular intervals (every 5th for example)

Question 5

What is Stratified Sampling?

Answer 5

Data is selected in proportion to ‘cluster’ sizes

Question 6

What is Opportunity (Convenience) Sampling?

Answer 6

Data is collected from whoever is available until sufficient data is obtained

Question 7

What is Quota Sampling?

Answer 7

Data is constantly selected until there is enough for the given category

Question 8

Method for Random Sampling (3):

Answer 8

1. Assign each date a number between 1 & 50
2. Using calculator, generate a number between 1 & 50 inclusive
3. Repeat process until you have 10 unique numbers

Question 9

Method for Systematic Sampling (4):

Answer 9

1. Select dates by highlighting one every so many down the list
2. 50 / 10 = 5
3. Choose a random starting point by using a random number generator within the first 5 dates of the list & highlight
4. highlight every 5th date down the list

Question 10

Method for Stratified Sampling (3):

Answer 10

1. Find the number of dates needed for each month
2. (no. of dates) / (total no. of dates) x number in sample
3. Select the appropriate number of dates using simple random sampling

Question 11

Method for Opportunity (Convenience) Sampling (2):

Answer 11

1. Take a sample from the people available at the time and fit the criteria you are looking for
2. e.g interview the first 20 people you see outside a supermarket carrying a shopping bag

Question 12

Method for Quota Sampling (2):

Answer 12

1. Interview each individual & allocate them to a group
2. When the quota for the group is filled, then ignore any further individuals fitting that group until all the quotas are met

Question 13

Advantage & Disadvantage of Random Sampling

Answer 13

+ All items of data equally likely to be selected
- Time consuming & Impractical on a large scale (requires a sampling frame)

Question 14

Advantage & Disadvantage of Systematic Sampling

Answer 14

+ Straightforward, Quick & Easy
- Requires a sampling frame

Question 15

Advantage & Disadvantage of Stratified Sampling

Answer 15

+ Reflects population fairly
- Time consuming & Impractical on a large scale (requires a sampling frame)

Question 16

Advantage & Disadvantage of Opportunity (Convenience) Sampling

Answer 16

+ Easy, No sampling Frame
- Unlikely to represent entire population

Question 17

Advantage & Disadvantage of Quota Sampling

Answer 17

+ Easy, No sampling Frame
- Population must be divided into groups, Can introduce bias

Question 18

How do you improve the reliability of a sample?

Answer 18

Increase the size of the sample (however there are cost implications)

Question 19

What is an Outlier?

Answer 19

An extreme value, 1.5 IQR’s beyond upper & lower quartiles

Question 20

What are Bar Charts used for? (3)

Answer 20

• Discrete Data
• Frequency = Bar heights
• Gaps between bars

Question 21

What are Histograms used for? (3)

Answer 21

• Continuous Data
• Frequency = Bar area
• No gaps between bars

Question 22

How to find Frequency Density?

Answer 22

Frequency / Class Width