Stats Sampling

Question 1

What is the population

Answer 1

Full set of things we are interested in

Question 2

What is a sample

Answer 2

As smaller set (subset) of the population

Question 3

What is a census

Answer 3

When data is collected about all members of the population

Question 4

What is a survey

Answer 4

When data is collected about a sub group of the population

Question 5

What is a parameter

Answer 5

A single number chosen to describe the entire population
Like the mean of population

Question 6

What is a statistic

Answer 6

A number calculated from a sample
Can be used to estimate the parameter

Question 7

What is the sampling frame

Answer 7

A list of the targeted population

Question 8

What is the method for a simple random sample (4)

Answer 8

Number everyone in the sampling frame
Use a random number generator to get the correct amount for the sample
Ignore repeats
Choose the people corresponding to the numbers

Question 9

What are 2 advantages of a random sample

Answer 9

Everyone has equal chance of selection so it’s considered a fair way of sampling

The sample is likely to be representative of the population

Question 10

What are 2 disadvantages of random sampling

Answer 10

Not possible without a sampling frame

Can be time consuming if large population is used

Question 11

How do you collect a stratified sample (3)

Answer 11

Divide the population into categories
Work out the proportion of each category required for the sample
Take a random sample from each category of the required number (list out steps of random sample in a an eq)

Question 12

2 advantages of stratified sampling

Answer 12

Minimise bias by making sure certain parts of population aren’t over or under represented

The frequencies for each group in the sample can be proportional to frequencies in the population

Question 13

2 disadvantage of stratified sampling

Answer 13

Not possible without a sampling frame

Sometimes difficult to split population into naturally occurring groups

Question 14

How do you carry out a systematic sample ? (2)

Answer 14

Take every nth unit which is calculated by doing population / sample

Pick a random starting point between 1 and n

Question 15

2 advantages of systematic sampling

Answer 15

Population is evenly sampled

Quick and easy to use

Question 16

2 disadvantage systematic sampling

Answer 16

Not possible without sampling frame

It’s not representative if the sampling technique coincides with a periodic trait

Question 17

What are 2 sampling techniques you use if you don’t have access to the whole population

Answer 17

Opportunity
Quota

Question 18

What is an opportunity sample

Answer 18

Taking data from a sample from what you have access to - those available at the time

Question 19

2 advantages opportunity sampling

Answer 19

Cheap

Quick and easy

Question 20

disadvantage opportunity sampling

Answer 20

It’s not random so it can be biased

Question 21

What is quota sampling

Answer 21

When the population is divided into groups like gender, age etc

A given number (quota) is surveyed from each group using opportunity sampling

Question 22

2 advantages quota sampling

Answer 22

Can be representative to population

No sampling frame required

Question 23

Disadvantage of quota sampling

Answer 23

Not random so it can be biased

Question 24

What is a sampling distribution

Answer 24

The values of a statistic and the associated probabilities

Question 25

Advantage and disadvantage of a census

Answer 25

Time consuming and expensive

Accurate cos it takes everyone into account