This function is just like `confidence-interval-t,' except that instead of its arguments being the actual data, it takes the following summary statistics: `mean,' which is the estimator of some t-distributed parameter; `dof,' which is the number of degrees of freedom in estimating the mean; and the `standard-error' of the estimator. In general, `mean' is a point estimator of the mean of a t-distribution, which may be the slope parameter of a regression, the difference between two means, or other practical t-distributions. `Confidence' should be a number between 0 and 1, exclusive.