辅导案例-STAT 231-Assignment 5

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STAT 231 Online Assignment 5

Download the Assignment 5 Template which is posted as a Word document in the
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The code for this assignment is posted both as a text file called
RCodeAssignment5.txt and an R file called RCodeAssignment5R.R
which are posted in the Assignment 5 folder on Learn.

Problem 1: Tests of hypothesis for Binomial data

The purpose of this problem is to use R to test the hypothesis
H0 :  = 0 for Binomial(n,) data. See Sections 5.1 and 5.3 of the
Course Notes, Example 5.3.1, and Chapter 5, Problem 1.

Run the following R code:
###################################################################################
# Problem 1: Tests of hypothesis for Binomial data
id<-20456484
set.seed(id)
# generate a random value of theta from a Uniform(0.3,0.35) distribution
theta<-round(runif(1,0.3,0.35),digits=3)
theta0<-round(theta+0.1,digits=1) # value for theta0
n<-30
y<-rbinom(1,n,theta) # observation from Binomial(n,theta) distribution
thetahat<-y/n #maximum likelihood estimate of theta
# display values
cat('theta = ', theta, ', theta0 = ',theta0, "\n")
cat('n = ', n, ', y = ', y, ', thetahat = ',thetahat, "\n")
# observed value of likelihood ratio test for testing the null hypothesis theta=theta0
lambda<--2*log((theta0/thetahat)^y*((1-theta0)/(1-thetahat))^(n-y))
cat('observed value of likelihood ratio statistic = ',lambda, "\n")
pvalue<-2*(1-pnorm(sqrt(lambda),0,1))
cat('approximate p-value for testing hypothesis theta = theta0: ',pvalue, "\n")
# observed value of approximate Gaussian test statistic for testing the null hypothesis theta=theta0
d<-abs(thetahat-theta0)/sqrt(theta0*(1-theta0)/n)
cat('observed value of approximate Gaussian test statistic = ',d, "\n")
pvalue<-2*(1-pnorm(d,0,1))
cat('approximate p-value for testing hypothesis theta = theta0: ',pvalue , "\n")
# exact p-value using test statistic D=|Y-n*theta0|
pvalue<-pbinom(y,n,theta0)+1-pbinom(n*theta0+abs(y-n*theta0)-1,n,theta0)
cat('exact p-value for testing hypothesis theta = theta0: ',pvalue, "\n")
###################################################################################


Verify that you obtain the following output:

theta = 0.316 , theta0 = 0.4

n = 30 , thetahat = 0.2333333

observed value of likelihood ratio statistic = 3.729682

approximate p-value for testing hypothesis theta = theta0: 0.05345357

observed value of approximate Gaussian test statistic = 1.86339

approximate p-value for testing hypothesis theta = theta0: 0.06240742

exact p-value for testing hypothesis theta = theta0: 0.09163583



Run the R code for again except modify the line
"id<-20456484"
by replacing the number 20456484 with your UWaterloo ID
number.
In the Assignment 5 template fill in the required information
based on the output for the data generated using your ID.

Modify the R code that you just used (the code with your ID
number inserted) so that n = 90 but theta, theta0, and thetahat
remain the same as for n = 30. (Note: you don’t need to generate
any new data.)
Run your modified code and fill in the required information in the
Assignment 5 template.


Problem 2: Tests of hypothesis for Poisson data

The purpose of this problem is to use R to test the hypothesis
H0 :  = 0 for Poisson() data. See Sections 5.1 and 5.3, and
Chapter 5, Problem 8 in the Course Notes.

Run the following R code:
###################################################################################
# Problem 2: Tests of hypothesis for Poisson data
id<-20456484
set.seed(id)
# generate a random value of theta from a Uniform(3,4) distribution
theta<-round(runif(1,3,4),digits=3)
theta0<-round(theta+0.6,digits=1) # value for theta0
n<-30
# determine the maximum likelihood estimate based on a random sample
# generated from a Poisson(theta) distribution
thetahat<-mean(rpois(n,theta))
# display values
cat('theta = ', theta, ', theta0 = ',theta0, "\n")
cat('n = ', n, ', thetahat = ',thetahat, "\n")
# observed value of likelihood ratio test for testing the null hypothesis theta=theta0
lambda<--2*log((theta0/thetahat)^(n*thetahat)*exp(n*(thetahat-theta0)))
cat('observed value of likelihood ratio statistic = ',lambda, "\n")
pvalue<-2*(1-pnorm(sqrt(lambda),0,1))
cat('approximate p-value for testing hypothesis theta = theta0: ',pvalue, "\n")
# observed value of approximate Gaussian test statistic for testing the null hypothesis theta=theta0
d<-abs(thetahat-theta0)/sqrt(theta0/n)
cat('observed value of approximate Gaussian test statistic = ',d, "\n")
pvalue<-2*(1-pnorm(d,0,1))
cat('approximate p-value for testing hypothesis theta = theta0: ',pvalue, "\n")
# exact p-value
d1<-n*abs(thetahat-theta0)
pvalue<-ppois(n*theta0-d1,n*theta0)+1-ppois(n*theta0+d1-1,n*theta0)
cat('exact p-value for testing hypothesis theta = theta0: ',pvalue, "\n")
###################################################################################


Verify that you obtain the following output:

theta = 3.326 , theta0 = 3.9

n = 30 , thetahat = 3.2

observed value of likelihood ratio statistic = 4.017457

approximate p-value for testing hypothesis theta = theta0: 0.04503156

observed value of approximate Gaussian test statistic = 1.941451

approximate p-value for testing hypothesis theta = theta0: 0.05220364

exact p-value for testing hypothesis theta = theta0: 0.05778636

Run the R code for again except modify the line
"id<-20456484"
by replacing the number 20456484 with your UWaterloo ID
number.
In the Assignment 5 template fill in the required information
based on the output for the data generated using your ID.



Problem 3: Tests of hypothesis for Exponential data

The purpose of this problem is to use R to test the hypothesis
H0 :  = 0 for Exponential() data. See Section 5.3, Example 5.3.2,
and Chapter 4, Problem 26 in the Course Notes.

Run the following R code:
###################################################################################
# Tests of hypothesis for Exponential data
id<-20456484
set.seed(id)
# generate a random value of theta from a Uniform(9,10) distribution
theta<-round(runif(1,9,10),digits=3)
theta0<-round(theta*1.3,digits=1) # value for theta0
n<-35
# determine the maximum likelihood estimate based on a random sample
# generated from a Exponential(theta) distribution
thetahat<-mean(rexp(n,1/theta))
# display values
cat('theta = ', theta, ', theta0 = ',theta0, "\n")
cat('n = ', n, ', thetahat = ',thetahat, "\n")
# observed value of likelihood ratio test for testing the null hypothesis theta=theta0
lambda<--2*log((thetahat/theta0)^n*exp(n*(1-thetahat/theta0)))
cat('observed value of likelihood ratio statistic = ',lambda, "\n")
pvalue<-2*(1-pnorm(sqrt(lambda),0,1))
cat('approximate p-value for testing hypothesis theta = theta0: ',pvalue, "\n")
# observed value of approximate Gaussian test statistic for testing the null hypothesis theta=theta0
d<-abs(thetahat-theta0)/(theta0/sqrt(n))
cat('observed value of approximate Gaussian test statistic = ',d, "\n")
pvalue<-2*(1-pnorm(d,0,1))
# exact p-value using test statistic D1=2n*thetatilde/theta0
cat('approximate p-value for testing hypothesis theta = theta0: ',pvalue, "\n")
d1<-2*n*thetahat/theta0
pvalue<-min(2*pchisq(d1,2*n),2*(1-pchisq(d1,2*n)))
cat('exact p-value for testing hypothesis theta = theta0 using D1: ',pvalue, "\n")
##################################################################################

Verify that you obtain the following output:

theta = 9.326 , theta0 = 12.1

n = 35 , thetahat = 9.293216

observed value of likelihood ratio statistic = 2.236861

approximate p-value for testing hypothesis theta = theta0: 0.1347543

observed value of approximate Gaussian test statistic = 1.372327

approximate p-value for testing hypothesis theta = theta0: 0.1699617

exact p-value for testing hypothesis theta = theta0 using D1: 0.1504173


Run the R code for again except modify the line
"id<-20456484"
by replacing the number 20456484 with your UWaterloo ID
number.
In the Assignment 5 template fill in the required information
based on the output for the data generated using your ID.

Modify the R code that you just used (the code with your ID
number inserted) so that n = 70 but theta, theta0, and thetahat
remain the same as for n = 35. (Note: you don’t need to generate
any new data.)
Run your modified code and fill in the required information in the
Assignment 5 template.

Problem 4: Tests of hypothesis for Gaussian data

The purpose of this problem is to use R to test the hypotheses
H0 : μ = μ0 and H0 : σ = σ0 for G(μ,σ) data. See Section 5.2 in the
Course Notes.

Run the following R code:
###################################################################################
# Problem 4: Tests of hypothesis for Gaussian data
id<-20456484
set.seed(id)
# generate a random value of mu from a Uniform(4,5) distribution
mu<-round(runif(1,4,5),digits=3)
mu0<-round(mu+1.25,digits=2) # value for mu0
# generate a random value of sigma from a Uniform(2,3) distribution
sigma<-round(runif(1,3,4),digits=3)
sigma0<-round(sigma*1.2,digits=1) # value for sigma0
n<-50
# determine the estimates based on a random sample
# generated from a G(mu,sigma) distribution
y<-rnorm(n,mu,sigma)
muhat<-mean(y)
s<-sd(y)
# display values
cat('mu = ', mu, ', mu0 = ',mu0, "\n")
cat('sigma = ', sigma, ', sigma0 = ',sigma0, "\n")
cat('n = ', n, ', muhat = ',muhat,', s = ',s, "\n")
# Use t.test fo test hypothesis mu=mu0
t.test(y,mu=mu0)$statistic
t.test(y,mu=mu0)$parameter
t.test(y,mu=mu0)$p.value
df<-length(y)-1
d<-df*s^2/sigma0^2
# observed value of statistic for testing the null hypothesis sigma=sigma0
cat('observed value of test statistic = ',d, "\n")
q<-pchisq(d,df)
# p-value for testing sigma=sigma0
cat('p-value for testing hypothesis sigma = sigma0 using D: ',min(2*q,2*(1-q)), "\n")
###################################################################################

Verify that you obtain the following output:

mu = 4.326 , mu0 = 5.58

sigma = 3.121 , sigma0 = 3.7

n = 50 , muhat = 4.542454, s = 2.787237

t
-2.632198

df
49

[1] 0.01131382

observed value of test statistic = 27.80613

p-value for testing hypothesis sigma = sigma0 using D: 0.01268351


Run the R code for again except modify the line
"id<-20456484"
by replacing the number 20456484 with your UWaterloo ID
number.
In the Assignment 5 template fill in the required information
based on the output for the data generated using your ID.

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