Calculating sample size for reducing standard error How to calculate a suitable sample size for reducing the standard error by a factor of 4? For instance if I have sample size of 1000 how much would I increase it to have a standard error reduced by 4?

$$
SE_1 =\dfrac{\sigma}{\sqrt n_1}\\
SE_2 =\dfrac{\sigma}{\sqrt n_2}
$$
You want $SE_1/SE_2=4$. Therefore, $
4=SE_1/SE_2=\dfrac{
\sigma/\sqrt{n_1}
}{
\sigma/\sqrt{n_2}
}
$. Now just do some algebra to get $n_2$ in terms of $n_1$.
