240 CHAPTER 5 Normal Probability Distributions Finding Area Under the Standard Normal Curve Find the area under the standard normal curve to the left of z = -0.99. SOLUTION The area under the standard normal curve to the left of z = -0.99 is shown. −0.99 z 0 Area = 0.1611 From the Standard Normal Table, this area is equal to 0.1611. Area to the left of z = -0.99 You can use technology to find the area to the left of z = -0.99, as shown below. EXCEL 0.16108706 =NORM.S.DIST(-0.99,TRUE) A 1 TRY IT YOURSELF 4 Find the area under the standard normal curve to the left of z = 2.13. Answer: Page A39 Finding Area Under the Standard Normal Curve Find the area under the standard normal curve to the right of z = 1.06. SOLUTION The area under the standard normal curve to the right of z = 1.06 is shown. 1.06 z 0 Area = 0.8554 Area = 1 − 0.8554 From the Standard Normal Table, the area to the left of z = 1.06 is 0.8554. Because the total area under the curve is 1, the area to the right of z = 1.06 is Area = 1 - 0.8554 = 0.1446. You can use technology to find the area to the right of z = 1.06, as shown at the left. TRY IT YOURSELF 5 Find the area under the standard normal curve to the right of z = -2.16. Answer: Page A39 EXAMPLE 4 EXAMPLE 5 EXCEL 0.1445723 =1-NORM.S.DIST(1.06,TRUE) A 1
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