Data Collection

Question 1

Define a population.

Answer 1

Population is a whole set of items which are of interest for data collection.

Question 2

What is a census?

Answer 2

A census is a method of observing and measuring every member of a population.

Question 3

Describe a sample.

Answer 3

A sample is a method where information from a subset of a population is used to find out information of the population as a whole.

Question 4

Give an advantage of a census.

Answer 4

The census is highly accurate, with its results taking into account a wide range of data.

Question 5

Give a disadvantage of a census.

Answer 5

It is very lengthy and expensive/costly to obtain data from a census.

Question 6

Describe another disadvantage of a census.

Answer 6

It is quite difficult to get data from a census due to a large amount of data required.

Question 7

Give an advantage of sampling.

Answer 7

Sampling is significantly less expensive to use than a census, and is much easier to use as well.

Question 8

Give another advantage of sampling.

Answer 8

Sampling requires fewer people for information on the population.

Question 9

Describe a disadvantage of sampling.

Answer 9

Because sampling requires fewer information, this means data won’t be enough to get information on the small subgroups/subsets of a population.

Question 10

List another disadvantage of sampling.

Answer 10

Data from sampling isn’t as accurate as data from a census.

Question 11

How does the size of the sample influence the validity of possible conclusions?

Answer 11

If a sample is of a large size, then this will make the data more accurate as there will be a higher quantity of data.

Question 12

How else does the size of the sample influence the validity of possible conclusions?

Answer 12

If there is some variation in the population, then to get information from the various subsets, a higher quantity of data is required here so a larger sample is needed.

Question 13

What is the name of individual units of a population?

Answer 13

Sampling units are the individual units of a population.

Question 14

What is a sampling frame?

Answer 14

A sampling frame is a list of numbered sample units or individually named sample units.

Question 15

What are the three types of random sampling?

Answer 15

• Simple random sampling
• Systematic sampling
• Stratified sampling

Question 16

Describe simple random sampling.

Answer 16

Simple random sampling is where a random member of a population is chosen, so in a population of n people, every sample of size n has a chance of being selected.

Question 17

How does simple random sampling measure the population?

Answer 17

A sampling frame is constructed with the population/items drawn up, each labeled with a unique number. Then at random, an item is chosen.

Question 18

Give some methods of measurement used for simple random sampling.

Answer 18

• Numbers randomly generated by a computer
• Random number table
  Or an extra method is using lottery sampling.

Question 19

Describe lottery sampling.

Answer 19

Lottery sampling is where the sampling units of the sampling frame are written on tickets and put into a hat, with the required number of tickets drawn out.

Question 20

What is systematic sampling?

Answer 20

Systematic sampling is another form of random sampling where a required elements are chosen at regular intervals from an ordered list.

Question 21

How does systematic sampling work?

Answer 21

Out of the whole population, a sample size is selected which consists of a certain number of the population (1/4, 1/2, 1/8 of population…), and every nth element is selected after the first element is selected at random;
if the sample size was 20 out of a population of 80, then as 80/4 = 20, the initial element is chosen at random but the elements that follow this are the fourth elements. For example, if the first element was 3, then the 2nd element is 3 + 4 = 7 and so on.

Question 22

What is stratified sampling?

Answer 22

Stratified sampling is another type of random sampling, where the population is sorted into mutually exclusive strata (level or class which people are designated to). The number of samples chosen in each stratum are the same.

Question 23

Give the formula of the number of samples in a stratum.

Answer 23

(number of items or people in stratum) / (number of items or people in population) x overall sample size.

Question 24

List an advantage of simple random sampling.

Answer 24

This method has no bias.

Question 25

Give another benefit of simple random sampling.

Answer 25

Simple random sampling is very useful for small population sizes or small sample sizes.

Question 26

Give a third benefit of simple random sampling.

Answer 26

In simple random sampling, there is a known equal chance of any member of the sample being chosen.

Question 27

What is a disadvantage of simple random sampling?

Answer 27

Simple random sampling isn’t so effective for large populations or large sample sizes.

Question 28

List another disadvantage of simple random sampling.

Answer 28

Simple random sampling requires creating a sampling frame. Sampling frames typically take a while to make as all sampling units (members of the sample) have to be labeled either by individually naming them or numbering them. This can be very time-consuming especially for large populations or sample sizes.

Question 29

What is an advantage of systematic sampling?

Answer 29

Systematic sampling is very effective for large populations and sample sizes as it divides large populations down into a smaller sample size.

Question 30

Give another advantage of systematic sampling.

Answer 30

Systematic sampling is fairly easy and quick to understand and use.

Question 31

What is a disadvantage of systematic sampling?

Answer 31

Systematic sampling requires creating a sampling frame.

Question 32

What is another disadvantage of systematic sampling?

Answer 32

After the first sampling unit is randomly chosen, the rest sampling units are chosen at regular not random intervals and this may increase risk of bias.

Question 33

What is an advantage of stratified sampling?

Answer 33

Stratified sampling accurately reflects the population structure.

Question 34

Give another advantage of stratified sampling.

Answer 34

Stratified sampling also guarantees a proportional representation of groups in a population.

Question 35

List a disadvantage of stratified sampling.

Answer 35

Like simple random sampling, stratified sampling isn’t so effective with a large population or sample size.

Question 36

What is another disadvantage of stratified sampling?

Answer 36

Stratified sampling involves organising data into mutually exclusive and distinctive strata (groups), and this can sometimes be difficult or time-consuming.

Question 37

What are the two types of non-random sampling?

Answer 37

• Quota sampling

- Opportunity sampling

Question 38

What is quota sampling?

Answer 38

Quota sampling is a form of non-random sampling, involving an interview or assessment of a population, splitting the population in groups according to a given characteristic.

Question 39

What is opportunity sampling?

Answer 39

Opportunity sampling is a type of non-random sampling where a sample is taken and people are available at the present moment and also meet the criteria.

Question 40

Give an advantage of quota sampling.

Answer 40

Quota sampling allows small samples to be representative of the whole population.

Question 41

Describe another advantage of quota sampling.

Answer 41

Quota sampling allows for an easy comparison between groups of data by splitting the population into groups.

Question 42

Give a third advantage of quota sampling.

Answer 42

Quota sampling is very simple, easy and inexpensive.

Question 43

What is a disadvantage of quota sampling?

Answer 43

Quota sampling is inaccurate as non-responses (those who don’t give full responses) are excluded from the sample.

Question 44

Give another disadvantage of quota sampling.

Answer 44

If the population is very large/if the data size is large, it can take lots of time and expertise to carry out the sampling. This is very time-consuming.

Question 45

What is an advantage of opportunity sampling?

Answer 45

Opportunity sampling is very easy as it just involves interviewing the first people you see who match your sample criteria.

Question 46

What is another advantage of opportunity sampling?

Answer 46

Opportunity sampling, like quota sampling, is very inexpensive.

Question 47

List a disadvantage of opportunity sampling.

Answer 47

Opportunity sampling isn’t so representative of the majority population as it takes place on a certain day, at a certain time of day and generally not many people are interviewed.

Question 48

Give another disadvantage of opportunity sampling.

Answer 48

Opportunity sampling is heavily dependent on the individual researchers, which isn’t good. This is because if one of the researchers misses some important data, then this may mess up quite a lot of the sampling.

Question 49

What is quantitative data?

Answer 49

Quantitative data/variable is a type of data which is associated with numerical observations; e.g. you can put a number on shoe size, or the weight of an object.

Question 50

What is qualitative data?

Answer 50

Qualitative data/variable is a type of data associated with non-numerical observations; e.g. you can’t put a number to the different colors of an apple (red and green) or names of cities in a country.

Question 51

What is continuous data?

Answer 51

Continuous data is a form of data which varies between quantities and accepts all types of data in a given range, regardless whether the number is an integer or decimal.
e.g. For the time taken to run a certain distance, as well as saying 5 seconds, you can also say 5.4 seconds or 5.32 seconds.

Question 52

What is discrete data?

Answer 52

Discrete data is a type of data which doesn’t vary and doesn’t accept values in a given range; instead it only takes specific values in a given range.
e.g. You can’t say you have 2.5 sons or daughters.

Question 53

What is used to represent large amounts of data?

Answer 53

A frequency table is used to contain large quantities/amounts of data.

Question 54

What does the midpoint in a frequency table demonstrate?

Answer 54

The midpoint is the average of the class boundaries.

Question 55

What do the class boundaries in a frequency table show?

Answer 55

The class boundaries show the maximum and minimum values of the class.

Question 56

What does the class width on a frequency table represent?

Answer 56

The class width is the difference between the upper and lower class boundaries.

Question 57

What is the mean daily temperature?

Answer 57

The mean daily temperature is the hourly temperature recorded, during a 24 hour period.

Question 58

Define the daily total rainfall.

Answer 58

The daily total rainfall is the total liquid and solid precipitation over a 24 hour period. For solid precipitation such as snow or hail, this must be melted. Amounts recorded less than 0.05 mm are simply recorded as trace or tr.