Data collection

Question 1

What is a population?

Answer 1

A whole set of items that are of interest.

Question 2

What is information obtained from a population known as?

Answer 2

Raw data

Question 3

What is a census?

Answer 3

A census observes or measures every member of a population.

Question 4

What are individual units of a population know as?

Answer 4

sampling units

Question 5

What is a simple random sample?

Answer 5

A simple random sample of size n is one where every sample of size n has an equal chance of being selected.

Question 6

What is stratified sampling?

Answer 6

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

Question 7

What is systematic sampling?

Answer 7

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

Question 8

What is quota sampling?

Answer 8

An interviewer or researcher selects a sample that reflects the characteristics of the whole population.

Question 9

What is opportunity sampling?

Answer 9

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

Question 10

What are three advantages of simple random sampling?

Answer 10

-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 11

What are two disadvantages of simple random sampling?

Answer 11

-It is not suitable when the population size or the sample size is large as it is it potentially time consuming, disruptive and expensive.

-A sampling frame is needed.

Question 12

What are two advantages of simple random sampling?

Answer 12

-It is simple and quick to use

-Suitable for large samples and large populations

Question 13

What are two disadvantages of systematic sampling?

Answer 13

-A sampling frame is needed

-It can introduce bias if the sampling frame is not random.

Question 14

What are two advantages of stratified sampling?

Answer 14

-Stratified sampling accurately reflects the population structure

-It guarantees proportional representation of groups within a population.

Question 15

What are two disadvantages of stratified sampling?

Answer 15

-The population must be clearly classified into distinct strata

-Selection within each stratum suffers from the same disadvantages as simple random sampling.

Question 16

What are three advantages of quota sampling?

Answer 16

-Allows a small sample to still be representative of the whole population.

-No sampling frame required.

-Quick, easy and inexpensive.

Question 17

What are three disadvantages of quota sampling?

Answer 17

-Quota sampling is a type of non-random sampling. So it can introduce bias.

-Population must be divided into groups, which can be costly or inaccurate.

-Increasing scope of study must be divided into groups, which can be costly or inaccurate.

Question 18

What are two advantages of opportunity sampling?

Answer 18

-It is easy to carry out

-Inexpensive

Question 19

What are two disadvantages of opportunity sampling?

Answer 19

-It is unlikely to provide an representative sample.

-Highly dependent on individual researcher.

Question 20

What is a sample?

Answer 20

Some subset of the population intended to represent the population.

Question 21

What is an advantage of a census?

Answer 21

A census should give completely accurate results.

Question 22

What are the disadvantages of a census?

Answer 22

-Time consuming and expensive

-Cannot be used when testing involves destruction.

-Large volume of data to process.

Question 23

What are the advantages of a sample?

Answer 23

-Cheaper

-Quicker

-Less data to process.

Question 24

What are the disadvantages of a sample?

Answer 24

-Data may not be accurate

-Data may not be large enough to represent small sub-groups.

Question 25

How do we carry out simple random sampling?

Answer 25

Allocate a number between 1 and N to each x (whatever is being tested)

Use a random number generator to select y (the sample) different numbers between 1 and N.

x corresponding to these numbers become the sample.

Question 26

How do we carry out systematic sampling?

Answer 26

Randomly select a number between 1 and pop size/sample (x) size and the select every xth person.

Question 27

How do we use stratified sampling?

Answer 27

Divide population into groups (strata) and carry and a simple random sample in each group.

Use when sample is large and population naturally divides into groups.

Question 28

How do we carry out quota sampling?

Answer 28

-Divide population into groups according to characteristics of interest, then determine the size of each group in a sample to reflect proportions within a population.

-Interviewer selects the actual sampling units.

Question 29

How do we carry out quota sampling?

Answer 29

-Interviewer selects the actual sampling units according to the set criteria.

Question 30

Main difference between random and non-random sampling?

Answer 30

-No sampling frame required for non-random sampling.

Question 31

What is discrete data?

Answer 31

-Can only take specific values (e.g. shoe size, can’t have a half a person etc)

Question 32

What is continuous data?

Answer 32

-Can take any decimal value.

Question 33

LDS less than you can treat <0.05mm as…

Answer 33

0

trace means 0