stats AS

Question 1

sample

Answer 1

set of data values for a random variable

Question 2

population

Answer 2

a group that you want to sample information about.

e.g. year 7 students in a school

Question 3

sampling frame

Answer 3

a collection of the items available to be sampled

e.g. a list of all the year 7 students in a school

Question 4

sample survey

Answer 4

when information is collected from a small representation of the population

Question 5

sampling unit

Answer 5

the person/object to be sampled

Question 6

sampling fraction

Answer 6

the proportion of available sampling units that are actually sampled

Question 7

census

Answer 7

when all the population has information collected about them

Question 8

simple random sampling

Answer 8

every item of the population has an equal chance of being picked

Question 9

opportunity/convenience sampling

Answer 9

sampling whatever/whenever its easiest

Question 10

stratified sampling

Answer 10

the population is divided into categories then a random sample is chosen from each category.
each categories size is proportional with the population.

Question 11

cluster sampling

Answer 11

the population is divided into strata representative of the population. a random sample of clusters is chosen and every item in the chosen clusters is sampled.

a large number of small clusters is most accurate.

Question 12

systematic sampling

Answer 12

every nth member is selected

Question 13

quota sampling

Answer 13

the population is divided into groups and a given number from each group is sampled.

Question 14

self-selecting sample

Answer 14

where people volunteer to taake part or are given a choice to participate.

may be bias as people may chose to express their opinions of certain matters.

Question 15

unimodal

Answer 15

one bump

Question 16

bimodal

Answer 16

two bumps

Question 17

positively skewed

Answer 17

bump near beginning

Question 18

negatively skewed

Answer 18

bump near end

Question 19

median

Answer 19

n+1/2

Question 20

frequency density

Answer 20

= frequency/ class width

Question 21

discrete Variables

Answer 21

can only take certain values but not those in between

Question 22

Bivariate data

Answer 22

two variables are assigned to each item

Question 23

Mean =

Answer 23

(Σxf)/n

Question 24

spearmans rank

Answer 24

shows association of the data

Question 25

Pearsons Product Moment correlation Coefficiant

Answer 25

a measure of correlation, r

Question 26

standard deviation

Answer 26

σ = sqrt (( (Σx^2)/n)- μ^2)

Question 27

standard deviation with frequency

Answer 27

σ = sqrt (( (Σx^2f)/Σf)- μ^2)

Question 28

outlier

Answer 28

a point more than two standard deviations away from the mean

Question 29

varience

Answer 29

σ^2

Question 30

P(A∨B) = | for mutually exclusive events

Answer 30

P(A)+P(B)

Question 31

P(A∨B) = | for not mutually exclusive events

Answer 31

P(A) + P(B) - P(A∧B)

Question 32

Independent events

Answer 32

events that have no effect on each other

Question 33

prove events are not idependent

Answer 33

P(A∧B) =/= P(A) x P(B)

Question 34

P(B|A)

Answer 34

probability of event B given that event A has happened

Question 35

if an event if independent

Answer 35

P(B|A) = P(B|A')

Question 36

P(A∧B) =

Answer 36

P(A) x P(B|A)

Question 37

how to run a simple random sample

Answer 37

- give a number to each population member - Generate a list of random numbers - Match these numbers to the population members to select the samples

Question 38

simple random sample advantage

Answer 38

every member of the population has an equal

Question 39

simple random sample disadvantage

Answer 39

it can be inconvenient if the population is spread over a large area

Question 40

how is a systematic sample carried out

Answer 40

- Give a number to each population member from a list of the full population - calculate a regular interval to use by dividing the population size by the sample size - generate a random starting point then follow the pattern

Question 41

systematic ample advantage

Answer 41

it can be used for quantity control on a production line. it should also give an unbiased sample. it relatively easy.

Question 42

systematic ample disadvantage

Answer 42

The regular interval could coincide with a pattern, giving a biased/unrepresentative distribution.

Question 43

opportunity/convenience advantage

Answer 43

data can be gathered very quickly and easily

Question 44

opportunity/convenience disadvantage

Answer 44

it isn't random and can't be very biased

Question 45

Stratified sampling advantage

Answer 45

if the population can be divided up into distinct categories, its likely to give a representative sample. different categories may differ and can be looked at independently.

Question 46

Stratified sampling disadvantage

Answer 46

its not useful when there aren't any obvious categories | it can be expensive because of the extra detail involved

Question 47

Quota sampling advantage

Answer 47

it can be done when there isn't a full list of the population. The sampler continues to sample people until they have enough

Question 48

Quota sampling disadvantage

Answer 48

can be easily biased by the sampler

Question 49

Cluster sampling advantage

Answer 49

more practical | can incorporate other sampling techniques

Question 50

Cluster sampling disadvantage

Answer 50

less representative of the population

Question 51

tow-stage cluster sample

Answer 51

randomly choose the samples then randomly select people from each cluster

Question 52

Normal distrubution

Answer 52

X~N(μ, σ^2)

Question 53

σ

Answer 53

standard deviation

Question 54

σ^2

Answer 54

varience

Question 55

Standard normal distrubution

Answer 55

Z~N(0,1)

Question 56

standard normal distrubution formula

Answer 56

Z = (X-μ)/σ

Question 57

test for normal approximation to binomial

Answer 57

np>5 | nq>5

Question 58

normal distrubution of a sample

Answer 58

~N(μ, σ^2/n)

Question 59

2/3 of normal distrubution

Answer 59

μ+-σ

Question 60

95% of normal distrubution

Answer 60

μ+-2σ

Question 61

99.7% of normal distrubution

Answer 61

μ+-3σ

Question 62

critical value for normal hypothesis test

Answer 62

μ+-k(σ/√n) | where k = Ф(significance level)