# SOLUTION: 1. Find the critical value zc necessary to form a confidence interval at 97% level of confidence

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 Click here to see ALL problems on Probability-and-statistics Question 272306: 1. Find the critical value zc necessary to form a confidence interval at 97% level of confidenceAnswer by Edwin McCravy(8911)   (Show Source): You can put this solution on YOUR website!``` This asks for the middle 97% or 0.97 of the data. Half of the middle 0.97 is to the right of z=0, and the other part is to the left of z=0 on the graph Half of 0.97 is 0.485. We look through the BODY of the normal table at this site http://business.statistics.sweb.cz/normal.jpg which should be just like the normal table in your book. You will find the listing 0.4850 near the bottom of the table on the right. You will notice at the far left of the row in which you find 0.4850 is the z value 2.1 and at the top of the column in which you find 0.4850 you'll find the value 0.07. You add those two numbers together 2.1+0.07 and get z=2.17. You know by symmetry of the normal curve, that the other half of the middle 97% is from z=-2.17 to z=0. So the critical values are z=-2.17 and z=2.17 Edwin```