Chapter 1 - Data Collection

Question 1

How can you define a population

Answer 1

The whole set of items that are of interest

Question 2

Define a sample

Answer 2

A sub-set of the population meant to represent the whole population

Question 3

What is a sampling unit

Answer 3

A single unit of the sample (for example if you have a sample of apples, one apple is a sampling unit)

Question 4

What are two methods to take data from a population

Answer 4

a sample and a census

Question 5

what does it mean to take a census

Answer 5

taking data from the entire population

Question 6

what are the advantages of a census

Answer 6

it provides fully accurate data about the population

Question 7

disadvantages of a census

Answer 7

it is costly, inefficient, and labour intensive due to the high volume of data needed to process
it does not work when the testing process destroys the item

Question 8

what are the advantages of testing a sample

Answer 8

it is less costly
it is more efficient
there is less data to process

Question 9

disadvantages of testing a sample

Answer 9

it may not be fully representative of the whole population

Question 10

what is a sampling frame

Answer 10

when sampling units are named or numbered individually into sub-sets or lists within the sample

Question 11

what are the 3 methods of random sampling

Answer 11

stratified sampling
systematic sampling
simple random sampling

Question 12

why must samples be taken randomly

Answer 12

to eliminate bias from the testing

Question 13

how can you define simple random sampling

Answer 13

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

Question 14

how can you carry out random sampling without bias

Answer 14

each unit in a sampling frame is assigned a unique number and a selection of these numbers is chosen at random
this can be done using a random number generator or a lottery system

Question 15

define a lottery system

Answer 15

a system where members of the sampling frame are written out on tickets and are placed into a “hat”
then the desired number of units is drawn at random

Question 16

how can you define systematic sampling

Answer 16

sampling in which the required units are chosen from a list at regular intervals

Question 17

how can you carry out systematic sampling

Answer 17

order the sampling units in a list, if the population is 100 and you need a sample size of 20, you need to take every (100÷20=) 5th unit in the list
the first person to be chosen should be random, so you need to generate a random number between 1 and 5 (in this case) to start with.
if 2 is generated, you choose the 2nd, 7th, 12th, 17th etc. unit

Question 18

what is stratified sampling

Answer 18

a population is divided into mutually exclusive strata (groups) (such as male and female) and a random sample is taken from each

Question 19

what calculation is needed to find out the number of people needed to be sampled from each strata

Answer 19

number sampled in a strata = (number in stratum ÷ number in population) × overall sample size

Question 20

advantages of random simple sampling

Answer 20

free of bias
every unit has an equal chance to be selected
simple and easy to implement for small populations

Question 21

disadvantages of simple random sampling

Answer 21

unsuitable when population or sample size is too large
sampling frame needed

Question 22

advantages of systematic sampling

Answer 22

simple to implement
suitable for large population and sample sizes

Question 23

disadvantages of systematic sampling

Answer 23

sampling frame is needed
may introduce bias if sample frame is not random

Question 24

advantages of stratified sampling

Answer 24

sample will accurately reflect the population structure
guarantees a proportional representation of groups within a population

Question 25

disadvantages of stratified sampling

Answer 25

population must initially be classed into defined strata
selection from each stratum suffers from the same disadvantages as simple random sampling

Question 26

what are the two methods of non random sampling

Answer 26

quota sampling
opportunity sampling

Question 27

describe quota sampling

Answer 27

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

Question 28

how do you carry out quota sampling

Answer 28

the population is divided into groups according to a characteristic, the size of the group determines the proportion of the sample that should have that characteristic
the interviewer meets, assesses and allocates each unit into the appropriate quota until all quotas are full
if a unit refuses to be interviewed, they are not counted as part of the data

Question 29

define opportunity sampling

Answer 29

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 for

Question 30

how do you carry out opportunity sampling

Answer 30

select the first people who are available or volunteer and use them as a sample to represent the population

Question 31

advs of quota sampling

Answer 31

allows a small sample to represent whole population accurately
no sampling frame required
quick, simple, inexpensive
allows for easy comparison between different groups within a population

Question 32

disadvs of quota sampling

Answer 32

may introduce bias as non random
population must be divided into groups - may be costly or inaccurate
increasing scope of study will increase number of groups which adds time or expense
non responses are not recorded

Question 33

disadvs of opportunity sampling

Answer 33

unlikely to provide a representative sample
highly dependent on individual researcher

Question 33

advs of opportunity sampling

Answer 33

easy
inexpensive

Question 34

what is quantitative data

Answer 34

numerical data (measured using numbers as values)

Question 35

what is qualitative data

Answer 35

non numerical data (colour, letter, shape etc.)

Question 36

what is continuous data
give examples

Answer 36

data which can take any value in a given range (including decimal values)
height, weight, length, time

Question 37

what is discreet data
give examples

Answer 37

data which can only take specific values in a range
number of people, shoe size, goals scored, correct answers on a test

Question 38

how does a frequency table display data

Answer 38

in one column, quantitative data is grouped into “classes” at the expense of losing the specific values
in the other column, the frequency (f) displays the number of instances in the class in the same row

Question 39

what do class bounds tell you

Answer 39

they indicate the lowest and highest values that belong to each class

Question 40

how can you find the midpoint of a class

Answer 40

add the class bounds and divide by 2 (the average of the bounds)