In reply to Coco.

In practice, you never know the "true value", so I cannot answer that question. However, it might be that you are trying to use the bootstrap for a statistic for which the bootstrap method is not appropriate. For example, the bootstrap does not work well for quantiles such as the median or the maximum.

In principle, there is nothing wrong with having an upper percentile equal to 100%. This could occur if you are trying to get a bootstrap CL for a proportion and the true proportion is fairly large (such as 0.9).

The bootstrap t interval is first order accurate whereas BCa is second-order accurate. I would not use the t interval unless the bootstrap distribution looks VERY normal.