Data Collection

Question 1

What is a population

Answer 1

In statistics, a population is the whole set of items that are of interest

Question 2

What is an example of a population

Answer 2

For example, the population could be the items manufactured by a factory or all the people in a town. Information can be obtained from a population

Question 3

What is raw data

Answer 3

Unprocessed information is known as raw data.

Question 4

What is a census

Answer 4

A census observes or measures every member of a population.

Question 5

What is a sample

Answer 5

A sample is 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 6

Advantage of a census

Answer 6

It should give a completely accurate result

Question 7

3 disadvantages of a sample

Answer 7

Time-consuming and expensive
Cannot be used when the testing process destroys the item
Hard to process a large quantity of data

Question 8

3 advantages of a sample

Answer 8

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

Question 9

2 disadvantages of a sample

Answer 9

Fewer people have to respond to give information about small sub-groups of the population
The data may not be as accurate

Question 10

The size of the sample depends on the required accuracy and available __________. Generally, the larger the sample, the more ________ it is, but you will need greater resources. If the population is very varied, you need a ______ sample than if the population were uniform. Different samples can lead to different conclusions due to the natural ______ in a population.

Resources, accurate, larger, variation

Answer 10

The size of the sample depends on the required accuracy and available resources. Generally, the larger the sample, the more accurate it is, but you will need greater resources. If the population is very varied, you need a larger sample than if the population were uniform. Different samples can lead to different conclusions due to the natural variation in a population.

Question 11

What is a sampling unit?

Answer 11

Individual units of a population are known as sampling units.

Question 12

What is a sampling frame?

Answer 12

Often sampling units of a population are individually named or numbered to form a list called a sampling frame.

Question 13

How does systematic sampling work?

Answer 13

In systematic sampling, the required elements are chosen at regular intervals from an ordered list.

Question 14

How could systematic sampling work if a sample size of 20 was required from a population of 100?

Answer 14

For example, if a sample of size 20 was required from a population of 100, you would take every fifth person since 100 / 20 = 5.

Question 15

How does stratified sampling work?

Answer 15

In stratified sampling, the population is divided into mutually exclusive strata (males and females, for example) and a random sample is taken from each. The proportion of each stratum sampled should be the same.

Question 16

What is a simple formula that can be used to calculate the number of people we should sample from each stratum

Answer 16

The number sampled in a stratum
—————————————————– x overall sample size number in the population

number in stratum

Question 17

Name 3 advantages of simple random sampling?

Answer 17

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

Question 18

Name 2 disadvantages of simple random sampling?

Answer 18

Not suitable when the population size or the sample size is large as it is potentially time-consuming, disruptive and expensive.
A sampling frame is needed

Question 19

Name 2 advantages of systematic sampling

Answer 19

• Simple and quick to use

* Suitable for large samples and large populations

Question 20

Name 2 disadvantages of systematic sampling

Answer 20

• A sampling frame is needed

* It can Introduce bias if the sampling frame Is not random

Question 21

Name 2 advantages of stratified sampling

Answer 21

• Sample accurately reflects the population structure

* Guarantees proportional representation of groups within a population

Question 22

Name 2 disadvantages of stratified sampling

Answer 22

• Population must be clearly classified into distinct strata
• Selection within each stratum suffers from the same disadvantages as simple random sampling

Question 23

What are the two types of non-random sampling that you need to know?

Answer 23

There are two types of non-random sampling that you need to know:
• Quota sampling
• Opportunity sampling

Question 24

In quota sampling, an interviewer or researcher selects a sample that reflects the ______ of the whole population. The population is divided into ____ according to a given characteristic. The size of each group determines the ______ of the sample that should have that characteristic. As an interviewer, you would meet people, assess their group and then, after the interview, allocate them into the appropriate quota. This continues until all ____ have been filled.

characteristics, groups, proportion, quotas,

Answer 24

In quota sampling, an interviewer or researcher selects a sample that reflects the characteristics of the whole population. The population is divided into groups according to a given characteristic. The size of each group determines the proportion of the sample that should have that characteristic. As an interviewer, you would meet people, assess their group and then, after the interview, allocate them into the appropriate quota. This continues until all quotas have been filled. If a person refuses to be interviewed or the quota into which they fit is full, then you simply ignore them and move on to the next person.

Question 25

When data is presented in a grouped frequency table, the specific data values are not shown. The groups are more commonly known as \_\_\_\_\_\_\_. 
• Class boundaries tell you the \_\_\_\_\_\_\_ and \_\_\_\_\_\_\_ values that belong in each class. 
• The midpoint is the \_\_\_\_\_\_\_ of the class boundaries. 
• The class width is the \_\_\_\_\_\_\_\_\_\_\_ between the upper and lower class boundaries.

Answer 25

When data is presented in a grouped frequency table, the specific data values are not shown. The groups are more commonly known as classes. 
• Class boundaries tell you the maximum and minimum values that belong in each class. 
• The midpoint is the average of the class boundaries. 
• The class width is the difference between the upper and lower class boundaries.