Sampling and Sample Data

Question 1

population

Answer 1

collection of objects with properties

Question 2

elements

Answer 2

the objects in the population

Question 3

cencus

Answer 3

a study of the whole population
often unfeasible due to numbers and limited resources

Question 4

sample

Answer 4

selection of one or more elements of the population

Question 5

statistical inference

Answer 5

understand the whole population by studying a sample from it

Question 6

representative sample

Answer 6

properties of sample match unknown properties of population

Question 7

non-representative sample

Answer 7

biased

Question 8

when is bias almost certain

Answer 8

samples are chosen from people who volunteer
samples are drawn from only part of a population
samples are chosen for their convenience
samples are selected by someone with a vested interest in the outcome

Question 9

how to avoid biased sampling

Answer 9

choose elements at random

Question 10

choosing at random

Answer 10

each element of the population has exactly the same chance of being selected

Question 11

what are the two ways of random sampling

Answer 11

with replacement and without replacement

Question 12

when do the two types of random sampling essentially become equivalent

Answer 12

when samples are much smaller than the population

Question 13

systematic sampling

Answer 13

elements selected according to a random starting point and a fixed periodic interval

Question 14

stratified sampling

Answer 14

useful when the population splits into distinct groups where the groups are quite different
together the groups cover the whole population

Question 15

cluster sampling

Answer 15

useful when the population splits into distinct clusters where the clusters are similar
take a random sample of clusters and then take the elements from within these clusters

Question 16

quota sampling

Answer 16

populations splits into many groups such as age, sex, income
only restricted by number of elements to be selected in each group

Question 17

variable

Answer 17

feature of the population of interest, takes a value for each element of the sample
denoted by a capital letter

Question 18

observation

Answer 18

each recorded value of a variable
denoted by a lower case letter corresponding to the variable

Question 19

sample data

Answer 19

collection of all observations derived from the sample
can be assembled in a data table

Question 20

categorical variables

Answer 20

non-numerical information such as names or labels which describe the possible attributes

Question 21

what are the two types of categorical variables

Answer 21

nominal or ordinal

Question 22

nominal variables

Answer 22

no inherent ordering of values

Question 23

ordinal variables

Answer 23

information about ordering or rank

Question 24

quantitative variables

Answer 24

provide numerical information

Question 25

what are the two types of quantitative variables

Answer 25

discrete or continuous

Question 26

discrete variables

Answer 26

can only take values from a certain set of distinct numbers

Question 27

continuous variables

Answer 27

take any value in an interval of numbers