When we speak of an "80% confidence level," what are we referring to? Multiple choice question. An interval which is within 80% of the standard deviation on either side of the mean. The point estimate An 80% probability that a parameter will be within a specified interval. We are confident that the parameter will be within 80% of the values found from the sample.Why is it important to know the population standard deviation when estimating the population mean? Multiple choice question. Knowing lets us use the standard normal distribution to construct a confidence interval. The mean is used in calculating the population standard deviation. The sample standard deviation cannot be used to estimate the population standard deviation