Equitailed confidence intervals of one sample.

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I am working on confidence intervals and would like to know if I did it correctly.

Let $X$ be a random variable. Find the $100(1-\alpha)$% CI for the parameter $\theta$ when

1), $X$ is Exponential with mean $\theta$.

2), $X$ is Uniform$(0,\theta)$.

3), $X_1, X_2, ..., X_n$ are iid Uniform$(0,\theta)$.

I simply used the inequality

$$a \le U \le b$$ $$Pr[U \le a]=\frac{\alpha}{2}$$ $$Pr[b \le U=\frac{\alpha}{2}$$

where $U=\frac{X}{\theta}$ is the pivot which resulted in

1), $\frac{X}{-\ln{(\alpha/2)}} \le \theta \le \frac{X}{-\ln{(1-\alpha/2)}}$

2), $\frac{X}{\alpha/2} \le \theta \le \frac{X}{1-\alpha/2}$

3), $\frac{X}{\sqrt[n]{\alpha/2}} \le \theta \le \frac{X}{\sqrt[m]{1-\alpha/2}}$

I have an exam in 2 days, it would be great if you could confirm or let me know if I made some mistake.

Thanks!