To find a critical value for z-scores, go to the Probability Calculator in Geogebra or the Probability Distribution plot in Minitab. Make sure you are using the standard Normal distribution (with = 0, = 1). Select a right-sided interval. For Geogebra: Convert the confidence level to decimal, and enter (1 - CL)/2 in the area/proportion box. This is what the text calls a/2. For example, a 95% confidence level would use (1.95)/2. Don't forget the parentheses! For Minitab (web): Select View Probability, then Options. Select Equal Tails. Convert the confidence level to decimal, and enter that value in for Probability. The critical value appear inside of P() (Geogebra) or under the normal curve (Minitab). Find the critical z-score value for each of the following confidence levels. Round each answer to four decimal places. The z-critical value for a(n) 70% confidence level is: The z-critical value for a(n) 80% confidence level is: . The z-critical value for a(n) 90% confidence level is: The z-critical value for a(n) 95% confidence level is: The z-critical value for a(n) 99% confidence level is: