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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.)

Find the z z -scores for which 15% 15 \% of the distribution's area lies between z -z and z z .\newlineThe z z -scores are \square .\newline(Use a comma to separate answers as needed. Round to two decimal places as needed.)

Full solution

Q. Find the z z -scores for which 15% 15 \% of the distribution's area lies between z -z and z z .\newlineThe z z -scores are \square .\newline(Use a comma to separate answers as needed. Round to two decimal places as needed.)
  1. Understand the problem: Understand the problem.\newlineWe need to find two z-scores such that the area between them under the standard normal distribution curve is 15%15\%. Since the normal distribution is symmetric, the area from z-z to zz will be split equally on both sides of the mean (which is 00 for a standard normal distribution). This means that 7.5%7.5\% of the area lies to the left of z-z and 7.5%7.5\% to the right of zz.
  2. Use the standard normal distribution table: Use the standard normal distribution table.\newlineTo 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%7.5\% (or 0.0750.075) of the area to the left of z-z, we need to find the z-score that corresponds to an area of 0.50.075=0.4250.5 - 0.075 = 0.425 to the left of it.
  3. Look up the z-score: Look up the z-score corresponding to an area of 0.4250.425. Using the standard normal distribution table, we find that the z-score that leaves an area of 0.4250.425 to its left is approximately 1.44-1.44. This is the z-score for z-z.
  4. Find the positive z-score: Find the positive z-score.\newlineSince the normal distribution is symmetric, the positive z-score +z+z that leaves an area of 0.5750.575 to its left (0.5+0.0750.5 + 0.075) will have the same absolute value as z-z. Therefore, +z+z is also approximately 1.441.44.
  5. Verify the solution: Verify the solution.\newlineWe have found that the z-scores are approximately 1.44-1.44 and 1.441.44. To verify, we can check that the area between these z-scores is 15%15\%. The area to the left of 1.441.44 is 0.5750.575, and the area to the left of 1.44-1.44 is 0.4250.425. The difference between these areas is 0.5750.425=0.150.575 - 0.425 = 0.15, which is 15%15\%. This confirms that our z-scores are correct.

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