Answer the questions about the specified normaldistribution a. The lifetime of Z

Question

Answer the questions about the specified normaldistribution a. The lifetime of ZZZ batteries are normally distributedwith a mean of 265 hours and a standard deviation 0 of 10hours. Find the number of hours that represent the 25thpercentile. b. Scores on an English placement test are normallydistributed with a mean of 39 and standard deviation 0 of 6.5. findthe scores that marks the top 10% Answer the questions about the specified normaldistribution a. The lifetime of ZZZ batteries are normally distributedwith a mean of 265 hours and a standard deviation 0 of 10hours. Find the number of hours that represent the 25thpercentile. b. Scores on an English placement test are normallydistributed with a mean of 39 and standard deviation 0 of 6.5. findthe scores that marks the top 10%

Explanation / Answer

a. You should look at a table of normal distribution to findthat the 25th percentile corresponds to approximately 0.67 standarddeviations away. Since Std. Dev is 10, 0.67 of this is 6.7hours. So, the 25th percentile will be all scores at or above(265 - 6.7) = 258.3 b. Same concept here: top 10% (or 90th percentile) correspondsto approx 1.65 standard deviations away. Thisequals 10.72 points. So the top 10% is all scores at orabove (39 + 10.72) = 49.72 points.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.