A random sample of 200 computers show that 12 computers have the defect. What critical value, z star, should Elena use to construct this confidence interval? So before I even ask you to pause this video, let me just give you a little reminder of what a critical value is. Remember, the whole point behind confidence intervals are we have some true population parameter. In this case, it is the proportion of computers that have a defect. So there's some true population proportion. We don't know what that is, but we try to estimate it.