The expected range is short by n minus 1 over n plus 1 and must be inflated

Let $X_1,X_2,\dots ,X_n(n\ge 3)$ be a random sample from the uniform distribution on the interval $({\theta }_1-{\theta }_2,{\theta }_1+{\theta }_2)$, where ${\theta }_1\in \mathbb{R}$ and ${\theta }_2>0$ are unknown parameters. Let $X_{(j)}$ be the jᵗʰ order statistic, j = 1, 2, …, n, and let $\bar{X}=(1/n){\sum }_i$₌${}_1^n{X}_i$. Here, $(X_{(1)},X_{(n)})$ is a complete and sufficient statistic for $({\theta }_1,{\theta }_2)$. Then, which of the following statements are true?