If, for a given sample size, 10% of all possible confidence intervals do not contain the unknown population parameter value, what is your confidence level?

To determine the confidence level, we need to consider the proportion of confidence intervals that do not contain the unknown population parameter value. In this case, we are told that 10% of all possible confidence intervals do not contain the true population parameter.

The confidence level represents the probability that a confidence interval will contain the true population parameter. Therefore, if 10% of confidence intervals do not contain the unknown population parameter, then the remaining 90% of confidence intervals must contain it.

Hence, the confidence level is 90%.