Let \(X_1,\ldots ,X_n\) be independent random variables with density functions \[ f(t,\theta _i)= \begin {cases} 0, & \text {if } t\notin [0,\infty ),\\ \dfrac {1}{\theta _i}e^{-t/\theta _i}, & \text {if } 0\leq t<\infty . \end {cases} \] We wish to test \(H_0:\theta _1=\theta _2=\cdots =\theta _n\) against the alternative that \(H_0\) is not true.
(a) Find a test using the likelihood ratio.
(b) Provide a large sample approximation for the likelihood ratio test.