Why cannot a confidence level be 100SolutionNOrmally even on

Why cannot a confidence level be 100%

Solution

NOrmally even one sample may deviate from the confidence interval due to external circumstances or war or some other abnormal causes.

Hence it is practically not possible to have 100% confidence interval.

The most useful estimates will be either 90%, or 95% or 99%

For medical fields 99% is the best and for other large things 90 or 95% may be ideal.