And so we'll often say this critical value, z, and this will be based on the number of standard deviations we wanna go above and below that statistic. And so then we'll multiply that times the standard deviation of the sampling distribution for that statistic. Now what we'll see is we often don't know this. To know this, you oftentimes even need to know this parameter. For example, in the situation where the parameter that we're trying to estimate and construct confidence intervals for is say the population proportion, what percentage of the population supports a certain candidate? Well, in that world, the statistic is the sample proportion. So we would have the sample proportion, plus or minus z star, times, well, we can't calculate this unless we know the population proportion.