Statistics

Question 1

population

Answer 1

the whole set of items that are of interest

Question 2

census

Answer 2

A census observes or measures every member of a population

Question 3

sample

Answer 3

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 4

sampling units

Answer 4

individual units of a population

Question 5

sampling frame

Answer 5

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

Question 6

census advantage(s)

Answer 6

it should give a completely accurate result

Question 7

census disadvantage(s)

Answer 7

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

Question 8

sample advantage(s)

Answer 8

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

Question 9

sample disadvantage(s)

Answer 9

• The data may not be as accurate

- The sample may not be large enough to give information about small sub-groups of the population

Question 10

random sampling

Answer 10

• every member of the population has an equal chance of being selected
• the sample should be representative of the population
• random sampling helps to remove bias from a sample

Question 11

Types of random sampling

Answer 11

• Simple random sampling
• Systematic sampling
• Stratified sampling

Question 12

simple random sampling

Answer 12

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

two methods

• lottery sampling
• generating random numbers

Question 13

systematic sampling

Answer 13

the required elements are chosen at regular intervals from an ordered list

Question 14

stratified sampling

Answer 14

the population is divided into mutually exclusive strata and a random sample is taken from each

the number sampled in a stratum = (number in stratum / number in population) x overall sample size

Question 15

simple random sampling advantage(s)

Answer 15

• 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 16

simple random sampling disadvantage(s)

Answer 16

• Not suitable when the population size or the sample size is large
• A sampling frame is needed

Question 17

systematic sampling advantage(s)

Answer 17

• simple and quick to use

- suitable for large samples and large populations

Question 18

systematic sampling disadvantage(s)

Answer 18

• a sampling frame is needed

- it can introduce bias if the sampling frame is not random

Question 19

stratified sampling advantage(s)

Answer 19

• sample accurately reflects the population structure

- guarantees proportional representation of groups within a population

Question 20

stratified sampling disadvantage(s)

Answer 20

• population must be clearly classified into distinct strata
• not suitable when the population size or the sample size is large
• a sampling frame is needed

Question 21

quota sampling

Answer 21

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

Question 22

opportunity sampling

Answer 22

Opportunity sampling 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 23

quota sampling advantage(s)

Answer 23

• Allows a small sample to still be representative of the population
• No sampling frame required
• Quick, easy and inexpensive
• Allows for easy comparison between different groups within a population

Question 24

quota sampling disadvantage(s)

Answer 24

• Non-random sampling can introduce bias
• Population must be divided into groups, which can be costly or inaccurate
• Increasing scope of study increases number of groups, which adds time and expense
• Non-responses are not recorded as such

Question 25

opportunity sampling advantage(s)

Answer 25

- easy to carry out | - inexpensive

Question 26

opportunity sampling disadvantage(s)

Answer 26

- unlikely to provide a representative sample | - highly dependent on individual researcher

Question 27

continuous variable

Answer 27

A variable that can take any value in a given range

Question 28

discrete variable

Answer 28

A variable that can only take specific values in a given range

Question 29

histogram, how to calculate heighe of each bar?

Answer 29

area of bar = k x frequency | k=1 is easiest to use when drawing histogram

Question 30

histogram frequency density

Answer 30

``` if k=1 then frequency density = frequency / class width ```

Question 31

What to comment on when comparing data sets?

Answer 31

- a measure of location | - a measure of spread

Question 32

independent and dependent variables

Answer 32

independent - the researcher could control this variable, plotted on x-axis dependent - the researcher measured this variable, plotted on y-axis

Question 33

how to work out mutually exclusive events?

Answer 33

P(A or B) = P(A) + P(B)

Question 34

how to work out independent events?

Answer 34

P(A and B) = P(A) x P(B)

Question 35

properties of a binomial distribution

Answer 35

- there are a fixed number of trials - there are two possible outcomes - there is a fixed probability of success - the trials are independent of each other