These wrapper functions compute the standard error (SE) or the confidence
interval (CI) of the values in `x`

. If `na.rm`

is `TRUE`

,
missing values are removed before the computation proceeds.

## Arguments

- x
a numeric vector or an R object which is coercible to one by

`as.vector(x, "numeric")`

.- na.rm
logical. Should missing values be removed?

- level
the confidence level required.

## See also

`sd()`

for the standard deviation.