STA 2212S 2023 HW Question 9
Hello, dear friend, you can consult us at any time if you have any questions, add WeChat: daixieit
HW Question 9
STA 2212S 2023
(a)Goodness- of-fit tests The data plotted in SM Figure 7.5 is computed from SM Table 1.1, and listed below. The values are the differences in height be- tween matched pairs of maize plants. The data can be read into R with scan(file="https://utstat.toronto.edu/reid/sta2212s/HW9data").
6.125, −8.375, 1, 2, 0.75, 2.875, 3.5, 5.125, 1.75, 3.625, 7, 3, 9.375, 7.5, −6
(i) Plot the empirical cumulative distribution function, and overlay the plot with a normal cdf where µ and σ 2 are estimated by the sample mean and variance.
(ii) Test the goodness-of-fit of the data to a normal distribution using the 1. Kolmogorov-Smirnov test, 2. the Cramer-vonMises test, and 3. the Anderson-Darling test. The first is available in base R as ks.test, and the other two are available in the package goftest.
(iii) Using the same data, create 4 bins determined by the quartiles of the data (e.g. use quantiles(x, c(.25,.5,.75))), and compute the χ2 goodness-of-fit statistic
where yj are the counts in the 4 bins, θˆ = ( , 2 ), = is the sample mean and 2 = (n − 1)− 1 Σ(xi − )2 is the sample variance.
(iv) Finally, compute the χ2 goodness-of-fit statistic with θ = (µ , σ 2 ) esti- mated by maximizing the multinomial likelihood function
Summarize the results of the goodness-of-fit tests in a small table.
(b) A non-regular problem: Suppose that (X1i , X2i), i = 1, . . . , n follow the bivariate normal distribution with expected value (θ1 , θ2 ) and identity covariance ma- trix: the joint distribution of the sample (x1 , x2 ) = (x11 , . . . , x1n , x21 , . . . , x2n) is then
The parameter space is restricted to θ 1 ≥ 0, θ2 ≥ 0.
(i) Show that the maximum likelihood estimators of θ 1 and θ2 are given by
(ii) Derive the form of the log-likelihood ratio statistic w = 2{ℓ(θˆ) − ℓ(θ0 )} for testing H0 : (θ1 , θ2 ) = (θ01 , θ02) = (0, 0).
(iii) Show that the distribution of w under H0 is
where 6{0} is a point mass at 0.
2023-03-20