statistics definitions

Question 1

population

Answer 1

the whole set of items that are of interest

Question 2

census

Answer 2

observes or measures every member of a population

Question 3

sample

Answer 3

a selection of observations taken from a subset of the population which is used to find out information about the population as a whole

Question 4

sampling units

Answer 4

Individual units of a population

Question 5

simple random sample

Answer 5

a simple random sample of size N is one where every sample of size N has an equal chance of being selected

Question 6

systematic sampling

Answer 6

in systematic sampling, the required elements are chosen at regular intervals from an ordered list

Question 7

stratified sampling

Answer 7

in stratified sampling, the population is divided into mutually exclusive strata(male and females for example) and a random sample is taken from each

Question 8

stratified sampling equation

Answer 8

number in strata/number in population x overall sample size

Question 9

advantages of simple random sampling

Answer 9

• free of bias
• easy and cheap to implement for small populations and samples
• each sampling unit has an equal chance of selection

Question 10

disadvantages of simple random sampling

Answer 10

• not suitable when the population size or the Sample size is to big.
• A sampling frame is needed

Question 11

advantages of systematic sampling

Answer 11

• simple and quick to use

- suitable for large samples and populations

Question 12

Disadvantages of systematic sampling

Answer 12

• sampling frame is needed

- can introduce bias if the sampling frame is not random

Question 13

Advantages of stratified sampling

Answer 13

• sample accurately reflects the population structure

- guarantees proportional representation of groups within a population.

Question 14

Disadvantages of stratified sampling

Answer 14

• population must be clearly classified into distinct strata

- suffers same disadvantages as simple random sampling for selection within each strata

Question 15

quota sampling

Answer 15

an interviewer or researcher sleds a sample that reflects the characteristics of the whole population

Question 16

Opportunity sampling

Answer 16

consists of taking the sample from people who are available at the time of the study and who fit the criteria

Question 17

Advantages of quota sampling

Answer 17

allows a small sample to still be representative of the population

• quick easy and inexpensive
• no sampling frame required

Question 18

disadvantages of quota sampling

Answer 18

• non responses are nor recorded as such

- increasing scope of study

Question 19

Advantages of opportunity sampling

Answer 19

• easy to carry out

- inexpensive

Question 20

Disadvantages of opportunity sampling

Answer 20

-highly dependent on individual researcher

Question 21

quantitative data

Answer 21

variables or data associated with numerical observations

eg: you can give a number to shoe sizes

Question 22

qualitative data

Answer 22

variables or data associated with non numerical observations

Question 23

continuous variable

Answer 23

this is a variable that can take any value in a given range and can be measured

Question 24

discrete variable

Answer 24

this is a variable that can only take specific values

Question 25

class boundary

Answer 25

max and min values that belong in each class

Question 26

midpoint

Answer 26

average of the class boundaries

Question 27

class width

Answer 27

difference between upper and lower class boundaries