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Let's say $A_n=O_p(n^{-3/5}\sqrt{log n})$. I wonder whether I can express $A_n$ as $o_p(n^{-2/5})$.Here's my attempt.

$$ P(\frac{|A_n|}{|n^{-3/5}\sqrt{log n}|} > \lambda) < \varepsilon $$ for all $n > M$ for some $M >0$. This implies that

$$P(|A_n| > \lambda \cdot n^{-2/5}n^{-1/5}\sqrt{log n}) < \varepsilon .$$

Since $lim_{n \rightarrow \infty} \frac{\sqrt{log n}}{n^{1/5}}=0$ by L'Hopital's rule, I can express the probability inequality as

$$P(\frac{|A_n|}{n^{-2/5}}> \varepsilon \prime) \rightarrow 0 .$$ Thus,

$$A_n=o_p(n^{-2/5}).$$ Am I right ?

Lee
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