Stats

Question 1

What is a population?

Answer 1

The whole set of items that are of interest

Question 2

What is a sampling frame?

Answer 2

A list where sampling units are individually named or numbered.

Question 3

Advantages and disadvantages of a census

Answer 3

+ve: gives a completely accurate result

-ve: time consuming, expensive, cannot be used if testing destroys the item, more data to process which is harder

Question 4

Advantages and disadvantages of simple random sampling

Answer 4

+ve: free of bias, easy and cheap, each sample unit has a known equal chance of selection.
-ve: not suitable when population size is large, sampling frame is needed

Question 5

Advantages and disadvantages of systematic sampling

Answer 5

+ve: simple and quick to use, suitable for large samples and populations
-ve: sampling frame is needed, can introduce bias if sampling frame is not random

Question 6

Advantages and disadvantages of stratified sampling

Answer 6

+ve: sample accurately reflects the population structure, guarantees proportional representation of groups within a population
-ve: population must be clearly classified into distinct strata, selection within each stratum has same -ve as simple random sampling

Question 7

Advantages and disadvantages of quota sampling

Answer 7

+ve: allows small sample to still be representative of the population, no sampling frame, quick easy inexpensive, allows for easy comparison between different groups within a population
-ve: non-random sampling can introduce bias, population must be divided into groups, non-responses are not recorded as such

Question 8

Advantages and disadvantages of opportunity sampling

Answer 8

+ve: easy to carry out, inexpensive

-ve: unlikely to provide a representative sample, highly dependent on individual researcher

Question 9

Define random

Answer 9

Where the outcome is not known until the experiment is carried out

Question 10

What is a random variable?

Answer 10

A variable whose value depends on the outcome of a random event

Question 11

Sample space

Answer 11

The range of values that a random variable can take

Question 12

Discrete

Answer 12

The variable is discrete if it can only take certain numerical values

Question 13

What is a probability distribution?

Answer 13

Something that fully describes the probability of any outcome in the sample space. Can be a probability mass function, a table or a graph

Question 14

Discrete uniform distribution

Answer 14

When all of the probabilities are the same in discrete data

Question 15

How to tell if two events are mutually exclusive

Answer 15

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

Question 16

How to tell if two events are independent

Answer 16

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

Question 17

When can you use binomial distribution?

Answer 17

When: 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

Question 18

What is the critical region?

Answer 18

A region of the probability distribution which, if the test statistic falls within it, would cause you to reject the null hypothesis.