Stats

Question 1

Random sampling

Answer 1

• Each member of the sample frame has an equal chance of being selected
• Number each member and then use a computer to calculate random numbers, the numbers that come out are then sampled

Question 2

Systematic sampling

Answer 2

• Uses a simple rule to choose people
• Can be a lot quicker than random for larger populations
• e.g. every 10th member is chosen to be sampled

Question 3

Stratified sampling

Answer 3

• Can be used when the population is split into groups that are likely to behave differently, e.g. children and adults favourite TV programme
• Each group sampled separately
• If children were to make up 20% of the population then we would make sure they make up 20% of the sample

Question 4

Quota sampling

Answer 4

• splitting the population into groups and sampling a given number of people from each group
• it doesn’t matter how the members of the sample are chosen as long as the quota is met
• if there is no sampling frame then this may be the only possible sampling method

Question 5

Population

Answer 5

A group we want to find info about

Question 6

Census

Answer 6

• When info about every member of the population is collected
• Can be difficult to accomplish if the population is large

Question 7

Sample survey

Answer 7

Is when info is collected from a small representation of the population

Question 8

Sampling unit

Answer 8

A person/object to be sampled

Question 9

Sampling frame

Answer 9

Is a collection of all the sampling units, ideally covering the whole population

Question 10

Mutually exclusive

Answer 10

Can’t happen at the same time
P(AuB) = P(A) +P(B)
P(AnB) = 0

Question 11

Independent events

Answer 11

The occurrence of one event does not influence the other
P(AuB) = P(A) + P(B) - P(AnB)
P(AnB) = P(A) × P(B)

Question 12

Spotting outliers

Answer 12

X +/- 2(SD)
or
Q1 - 1.5IQR
Q3 + 1.5IQR