Chapter 3

Methods for Constructing Point Estimates of Parameters

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Problem 3.1

Prove that the parameter estimators constructed in Examples 3.1 and 3.3 are asymptotically unbiased and strongly consistent.

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Problem 3.2

A sample of size nn is generated by the random variable X∼Exp⁡(θ),θ>0X \sim \operatorname {Exp}\left(\theta \right), \theta > 0. Find the ML estimator of the parameter θ\theta and prove its strong consistency.

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Problem 3.3

A sample of size nn corresponds to the Poisson distribution Pois⁡(θ)\operatorname {Pois}\left(\theta \right), θ>0\theta > 0. Find the ML estimator of θ\theta and prove its unbiasedness, strong consistency, and asymptotic normality.

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Problem 3.4

The sample {Xk,k=1,…,n}\left\{ X_{k}, k = 1, \ldots , n\right\} is generated by the random variable X∼E(θ1,θ2),θ2>0X \sim E(\theta_{1}, \theta_{2}), \theta_{2} > 0, i.e.

pX(x)={θ2exp⁡{−θ2(x−θ1)}, if x⩾θ1,0, if x<θ1. p_{X}(x) = \begin{cases} \theta _{2} \exp \left\{ -\theta _{2}\left(x-\theta _{1}\right)\right\} , & \text{ if } x \geqslant \theta _{1}, \\ 0, & \text{ if } x < \theta _{1} .\end{cases}

Find estimators of the parameters θ1\theta_{1} and θ2\theta_{2} by the method of moments. Prove the strong consistency of the obtained estimators.

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Problem 3.5

The sample ZnZ_{n} corresponds to the Rayleigh distribution with distribution function F(x;θ)=1−exp⁡{−x2θ},x⩾0,θ>0F(x ; \theta ) = 1-\exp \left\{ -\frac{x^{2}}{\theta }\right\} , x \geqslant 0, \theta > 0. Find the ML estimator of the parameter θ\theta.

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Problem 3.6

The sample Zn={Xk,k=1,…,n}Z_{n} = \left\{ X_{k}, k = 1, \ldots , n\right\} of size n=2m+1n = 2 m+1 (mm is a natural number) corresponds to the Laplace distribution with density p(x;θ)=12exp⁡{−∣x−θ∣}p(x ; \theta ) = \frac{1}{2} \exp \left\{ -\left|x-\theta \right|\right\}. Find the ML estimator of the parameter θ\theta.

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Problem 3.7

Under the conditions of Problem 6, for the case n=2mn = 2 m, show that any statistic of the form θ^n=(1−λ)X(m)+λX(m+1),λ∈[0;1]\widehat{\theta }_{n} = (1-\lambda ) X_{(m)}+\lambda X_{(m+1)}, \lambda \in [0 ; 1] is an ML estimator of θ\theta.

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Problem 3.8

Let θ^n\widehat{\theta }_{n} be the ML estimator of the parameter θ\theta of the Bernoulli distribution Bin⁡(1,θ)\operatorname {Bin}\left(1, \theta \right). Show that the sequence n(θ^n−θ)\sqrt{n}\left(\widehat{\theta }_{n}-\theta \right) is asymptotically normal with parameters (0;θ(1−θ)0 ; \theta (1-\theta )).

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Problem 3.9

The sample ZnZ_{n} corresponds to the normal distribution with parameters (θ;2),θ⩾0(\sqrt{\theta } ; 2), \theta \geqslant 0. Find the ML estimator of θ\theta.

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Problem 3.10

The sample Zn={Xk,k=1,…,n}Z_{n} = \left\{ X_{k}, k = 1, \ldots , n\right\} corresponds to the lognormal distribution with parameters (θ1;θ2)\left(\theta_{1} ; \theta_{2}\right), i.e. ln⁡Xk∼N(θ1;θ2)\ln X_{k} \sim \mathcal{N}\left(\theta_{1} ; \theta_{2}\right). Find the ML estimator of the parameter θ=E[Xk]\theta = \mathbb {E}\left[X_{k}\right] and prove its strong consistency.

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Problem 3.11

Find the ML estimator of the parameter θ=E[Xk]\theta = \mathbb {E}\left[X_{k}\right] from the sample {Xk,k=1,…,n}\left\{ X_{k}, k = 1, \ldots , n\right\} corresponding to the distribution R[θ1,θ2]R\left[\theta_{1}, \theta_{2}\right].

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