Question 2, 5.3.30Pointsx Points: 0 of 1Find the z-scores for which 15% of the distribution's area lies between −z and z.Click to view pace lof the table Click to view page 2 of the table.The z-scores are □.(Use a comma to separate answers as needed. Round to two decimal places as needed.)
Q. Question 2, 5.3.30Pointsx Points: 0 of 1Find the z-scores for which 15% of the distribution's area lies between −z and z.Click to view pace lof the table Click to view page 2 of the table.The z-scores are □.(Use a comma to separate answers as needed. Round to two decimal places as needed.)
Understand total distribution area: To find the z-scores for which 15% of the distribution's area lies between −z and z, we need to understand that the total area under the standard normal distribution curve is 1 (or 100%). Since we are looking for the area in the middle of the curve, we need to first determine the area in one tail to exclude.
Calculate excluded tail area: The area we want to exclude from each tail is half of 15%, because we are looking for the area between −z and z, which is symmetrical around the mean. So, we calculate 15%/2=7.5% for each tail.
Find z-score for 85% distribution: Now we need to find the z-score that corresponds to the area to the left of z that includes the middle 85% of the distribution (100%−15%=85%). Since the distribution is symmetrical, we want the area to the left of z to be 85%/2=42.5% plus the 7.5% in the lower tail, which totals 50%.
Lookup z-score for 0.9250 area: Using a standard normal distribution table or a calculator with inverse normal distribution function, we look up the z-score that corresponds to an area of 0.5000+0.4250=0.9250 to the left of z.
Identify positive and negative z-scores: The z-score that corresponds to an area of 0.9250 to the left is approximately 1.44. This is the positive z-score. Since the normal distribution is symmetrical, the negative z-score is −1.44.
Final z-scores for 15% area: Therefore, the z-scores for which 15% of the distribution's area lies between −z and z are approximately −1.44 and 1.44.
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