Statistics

Question 1

Population

Answer 1

The whole set of items that are of interest

Question 2

Sample

Answer 2

Small subset of the population intended to represent the whole population

Question 3

Advantages & Disadvantages of a census

Answer 3

Advantages - completely accurate
Disadvantages - time consuming

Question 4

Advantages & Disadvantages of a sample

Answer 4

Advantages - quick & cheap
Disadvantages - may not be accurate or large enough to represent small sub-groups

Question 5

Sampling unit

Answer 5

Each thing in a population that can be sampled

Question 6

Sampling frame

Answer 6

When sampling units of a population are individually numbered to form a list

Question 7

Simple random sampling

Answer 7

Each item is numbered and use a generator - each one has an equal chance of being selected

Question 8

Advantages of simple random sampling

Answer 8

Bias free, easy & cheap, equal chance of selection

Question 9

Disadvantages of simple random sampling

Answer 9

Needs a sampling frame, not suitable for large population

Question 10

Systematic sampling

Answer 10

First item randomly chosen then they are chosen at regular intervals

Question 11

Systematic sampling formula

Answer 11

K(regular interval) = pop size (N) / sample size (n)

Question 12

Advantages of systematic sampling

Answer 12

Simple and quick for large samples/populations

Question 13

Disadvantages of systematic sampling

Answer 13

Sampling frame needed, can introduce bias if not random

Question 14

Stratified sampling

Answer 14

Population divided into groups(strata) and a simple random sample in each group

Question 15

Stratified sampling formula for each strata

Answer 15

(Sample size (n) / Population size (N)) x strata size

Question 16

Advantages of Stratified sampling

Answer 16

Used in large sample, guarantees proportional representation of groups within population

Question 17

Disadvantages of stratified sampling

Answer 17

Population has to be classified into distinct strata
Each strata has the same problems as random sampling disadvantages

Question 18

Quota sampling

Answer 18

Population is divided into groups(age, gender etc…)
A given no is surveyed from each group

Question 19

Advantages of quota sampling

Answer 19

Cheap and done quickly and accurately

Question 20

Disadvantages of quota sampling

Answer 20

Not random sampling, not unbiased

Question 21

Convenience sampling

Answer 21

Most convenient sample is chosen e.g for a sample of 60 it’s the first 60 people you meet

Question 22

Convenience sampling advantages

Answer 22

Convenient and quick

Question 23

Convenience sampling disadvantages

Answer 23

Biased and doesn’t truly represent population