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3.4 Optional application 2 – statistics

3.4.1 SA: Discrete random variables (DRVs) and expectation

 
Content
SA1
Understand DRVs with distributions given in the form of a table or function.
 
Content
SA2
Evaluate probabilities for a DRV.
 
Content
SA3
Evaluate measures of average and spread for a DRV to include mean, variance, standard deviation, mode and median.
 
Content
SA4
Understand expectation and know the formulae:
EX=xipi
;
EX2=xi2pi
;
VarX=EX2-(EX)2
 
Content
SA5

Understand expectation of linear functions of DRVs and know the formulae:

EaX+b=aEX+b
and
VaraX+b=a2Var(X)

Know the formula

EgX=g(xi)pi

Find the mean, variance and standard deviation for functions of a DRV such as

E5X3,E18X-3,Var(6X-1)

 
Content
SA6

Know the discrete uniform distribution defined on the set

1,2,,n
. Understand when this distribution can be used as a model.

3.4.2 SB: Poisson distribution

 
Content
SB1

Understand conditions for a Poisson distribution to model a situation. Understand terminology

X~Po(λ)
.

 
Content
SB2
Know the Poisson formula and calculate Poisson probabilities using the formula or equivalent calculator function.
 
Content
SB3

Know mean, variance and standard deviation of a Poisson distribution.

Use the result that, if

X~Poλ
then the mean and variance of
X
are equal.

 
Content
SB4
Understand the distribution of the sum of independent Poisson distributions.
 
Content
SB5

Formulate hypotheses and carry out a hypothesis test of a population mean from a single observation from a Poisson distribution using direct evaluation of Poisson probabilities.

3.4.3 SC: Type I and Type II errors

 
Content
SC1

Understand Type

I
and Type
II
errors and define in context. Calculate the probability of making a Type
I
error from tests based on a Poisson or Binomial distribution.

Calculate probability of making Type

I
error from tests based on a normal distribution.

 
Content
SC2

Understand the power of a test. Calculations of P(Type

II
error) and power for a test for tests based on a normal, Binomial or a Poisson distribution.

3.4.4 SD: Continuous random variables (CRVs)

 
Content
SD1
Understand and use a probability density function,
f(x)
, for a continuous distribution and understand the differences between discrete and continuous distributions.
Understand and use distributions of random variables that are part discrete and part continuous.
 
Content
SD2
Find the probability of an observation lying in a specified interval.
 
Content
SD3
Find the median and quartiles for a given probability density function,
f(x)
.
 
Content
SD4

Find the mean, variance and standard deviation for a given pdf,

f(x)
. Know the formulae

EX=xfxdx
,
EX2=x2fxdx
,
VarX=EX2-(EX)2

 
Content
SD5

Understand the expectation and variance of linear functions of CRVs and know the formulae:

EaX+b=aEX+b
and
VaraX+b=a2Var(X)

Know the formula

EgX=gxf(x)dx

Find the mean, variance and standard deviation of functions of a continuous random variable such as

E5X3,E18X-3,Var(6X-1)

 
Content
SD6

Understand and use a cumulative distribution function,

F(x)
. Know the relationship between
f(x)
and
F(x)
.

Fx=-xftdt
and
fx=ddxFx

Content
SD7
Understand the rectangular distribution
f(x)
where

f(x)={1baaxb0otherwise

Know the conditions for the rectangular distribution to be used as a model.

Calculate probabilities from a rectangular distribution.

Know proofs of mean, variance and standard deviation for a rectangular distribution.

 
Content
SD8

Know that if

X
and
Y
are independent (discrete or continuous) random variables then
EX+Y=EX+EY
and
VarX+Y=VarX+Var(Y)

3.4.5 SE: Chi squared tests for association

 
Content
SE1
Construction of
n
×
m
contingency tables.
 
Content
SE2

Use of

(Oi-Ei)2Ei
as an approximate
χ2
statistic with appropriate degrees of freedom.

 
Content
SE3
Know and use the convention that all
Ei
should be greater than 5.
 
Content
SE4
Identification of sources of association in the context of a question.
 
Content
SE5
Knowledge of when and how to apply Yates’ correction.

3.4.6 SF: Exponential distribution

 
Content
SF1
Know the conditions for an exponential distribution to be used as a model. Know the probability density function,
f(x)
, and the cumulative distribution function,
F(x)
, for an exponential distribution.
 
Content
SF2
Calculate probabilities for an exponential distribution using
F(x)
or integration of
f(x)
 
Content
SF3
Know proofs of mean, variance and standard deviation for an exponential distribution.
 
Content
SF4
Understand that the lengths of intervals between Poisson events have an exponential distribution.

3.4.7 SG: Inference – one sample t- distribution

 
Content
SG1

Test for the mean of a normal distribution with unknown variance using a

t
with appropriate degrees of freedom.

3.4.8 SH: Confidence Intervals

 
Content
SH1

Construct symmetric confidence intervals for the mean of a normal distribution with known variance.

 
Content
SH2
Construct symmetric confidence intervals from large samples, for the mean of a normal distribution with unknown variance.
 
Content
SH3
Make inferences from constructed or given confidence intervals.
 
Content
SH4
Construct symmetric confidence intervals from small samples, for the mean of a normal distribution with unknown variance using the
t
-distribution.