Find the z-scores for which 15% of the distribution's area lies between −z and z.The z-scores are □.(Use a comma to separate answers as needed. Round to two decimal places as needed.)
Q. Find the z-scores for which 15% of the distribution's area lies between −z and z.The z-scores are □.(Use a comma to separate answers as needed. Round to two decimal places as needed.)
Understand the problem: Understand the problem.We need to find two z-scores such that the area between them under the standard normal distribution curve is 15%. Since the normal distribution is symmetric, the area from −z to z will be split equally on both sides of the mean (which is 0 for a standard normal distribution). This means that 7.5% of the area lies to the left of −z and 7.5% to the right of z.
Use the standard normal distribution table: Use the standard normal distribution table.To find the z-scores, we will use the standard normal distribution table, which gives us the area to the left of a given z-score. Since we want 7.5% (or 0.075) of the area to the left of −z, we need to find the z-score that corresponds to an area of 0.5−0.075=0.425 to the left of it.
Look up the z-score: Look up the z-score corresponding to an area of 0.425. Using the standard normal distribution table, we find that the z-score that leaves an area of 0.425 to its left is approximately −1.44. This is the z-score for −z.
Find the positive z-score: Find the positive z-score.Since the normal distribution is symmetric, the positive z-score +z that leaves an area of 0.575 to its left (0.5+0.075) will have the same absolute value as −z. Therefore, +z is also approximately 1.44.
Verify the solution: Verify the solution.We have found that the z-scores are approximately −1.44 and 1.44. To verify, we can check that the area between these z-scores is 15%. The area to the left of 1.44 is 0.575, and the area to the left of −1.44 is 0.425. The difference between these areas is 0.575−0.425=0.15, which is 15%. This confirms that our z-scores are correct.