Math  /  Data & Statistics

Question6 5/5 points Let X1,X2,,XnX_{1}, X_{2}, \ldots, X_{n} be independent and identically distributed random variables from a uniform distribution on the interval (0,a)(0, a). The value of a is unknown. Derive the method of moments estimate of the parameter a. 2(X1++Xn)/n2\left(X_{1}+\ldots+X_{n}\right) / n 2* median( X1,,Xn\mathrm{X} 1, \ldots, \mathrm{Xn} ) Max(X1,X2,,Xn)\operatorname{Max}\left(X_{1}, X_{2}, \ldots, X_{n}\right)

Studdy Solution

STEP 1

What is this asking? Find a way to estimate the unknown maximum value aa from a uniform distribution using the method of moments. Watch out! Don't confuse the method of moments with other estimation methods like maximum likelihood!

STEP 2

1. Understand the uniform distribution
2. Calculate the expected value
3. Set up the method of moments equation
4. Solve for the estimate of aa

STEP 3

Alright, let's get into it!
We're dealing with a **uniform distribution** on the interval (0,a)(0, a).
This means every value between 00 and aa is equally likely.
It's like picking a random number from a perfectly shuffled deck of cards, where each card represents a number between 00 and aa.

STEP 4

Now, let's talk about the **expected value** of a uniform distribution on (0,a)(0, a).
The expected value, or mean, is the average value you'd expect if you could sample an infinite number of times.
For a uniform distribution, the expected value is given by:
E(X)=a2E(X) = \frac{a}{2}
This formula tells us that the average value is right in the middle of the interval from 00 to aa.

STEP 5

The **method of moments** is a way to estimate parameters by equating sample moments to theoretical moments.
Here, we equate the sample mean to the expected value of the distribution.
So, if we have a sample mean Xˉ\bar{X}, we set:
Xˉ=a2\bar{X} = \frac{a}{2}
This equation is our bridge from the sample data to the unknown parameter aa.

STEP 6

Let's solve for aa by rearranging the equation from the previous step.
Multiply both sides by 2 to isolate aa:
a=2Xˉa = 2 \cdot \bar{X}
This gives us the **method of moments estimate** for aa.
It's as simple as doubling the sample mean!

STEP 7

The method of moments estimate for the parameter aa is given by:
a=2Xˉa = 2 \cdot \bar{X}

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