Statistics

Question 1

What is a census?

Answer 1

Measures every member of a population

Question 2

What is a sample?

Answer 2

Observations taken from a subset of a population to get information about the whole.

Question 3

Advantages of census

Answer 3

Completely accurate

Question 4

Disadvantages of census

Answer 4

Time and money consuming, impossible if process involves destroying the subject, hard to process loads of data

Question 5

Advantages sample

Answer 5

Less data, less time and money consuming, less subjects needed.

Question 6

Disadvantages sample

Answer 6

May not be accurate, not large enough

Question 7

Simple random sampling

Answer 7

Assign number to each unit then randomly pick

Question 8

Systematic sampling

Answer 8

Chosen at regular intervals through a list with the position of where you start random

Question 9

Stratified sampling

Answer 9

Proportionally picked from each group

Question 10

Advantages of simple random sampling

Answer 10

No bias, easy/cheap

Question 11

Disadvantages of random sampling

Answer 11

Not suitable for large groups, sampling frame required

Question 12

Systematic sampling advantages

Answer 12

Simple, quick, good for large groups

Question 13

Systematic sampling disadvantages

Answer 13

Sampling frame needed, can introduce bias if frame is not random

Question 14

Stratified sampling advantages

Answer 14

Accurately represents population structure, guarantees that proportional representation

Question 15

Stratified sampling disadvantages

Answer 15

Must be pre-classified into strata, selection has same issues as simple random sampling.

Question 16

Quota sampling

Answer 16

Sampler selects which group the person is put in and ignores when quota is full

Question 17

Opportunity sampling

Answer 17

Take a sample if the unit suits criteria and is available

Question 18

Quota sampling advantages

Answer 18

Small sample still representative, no frame

Question 19

Quota sampling disadvantages

Answer 19

Can be biased, division into groups may be inaccurate and costly

Question 20

Opportunity sample advantages

Answer 20

Easy, cheap

Question 21

Opportunity sampling disadvantages

Answer 21

Dependent on sampler and unlikely to give representative sample

Question 22

Measure of location

Answer 22

Value that describes a position in a data set

Question 23

Measure of central tendency

Answer 23

Single value describing the centre of the data (mean, median, mode)

Question 24

When working out lower and upper quartiles how do you round?

Answer 24

UP

Question 25

Histograms

Answer 25

Frequency density = frequency/class width

Question 26

Bivariate data

Answer 26

Pairs of values for two variables (one independent and one dependent variable)

Question 27

What is the least squares regression line?

Answer 27

Line of best fit

Question 28

Discrete uniform distribution

Answer 28

The probability of each outcome is the same (e.g. a fair die)

Question 29

Conditions for binomial distribution

Answer 29

Fixed number of trials, two possible outcomes, fixed probability, independent

Question 30

How to measure outliers?

Answer 30

1.5 x IQR below/above LQ/UQ

Question 31

How to check whether two events are independent?

Answer 31

P(A and B) = P(A) × P(B) if independent