Suppose we are about to draw a sample from a normally distributed population, and find a confidence interval for the population mean. Which one of the following statements is true? 95% of the observations in the sample will fall within the 95% confidence interval we calculate. The t approach is always used when the population standard deviation is known. All else being equal, the greater the variance, the smaller the margin of error. If we use a z value when calculating the interval when we should be using t, the resulting interval will be too wide. A 99% confidence interval will be wider than the corresponding 95% interval calculated on the same data