the scores on a qualifyign exam for entrance into a post secondary school are normally distributed with a mean of 120 and a standard deviation of 10.5. To qualify for admittance, the candidates must score in the top 10%. Find the lowest possible score to qualify.
I got stuck on this question when reviewing for finals. Can someone help me with this? Thank you
probability and calculus question?
2009-03-03 7:52 am
回答 (2)
2009-03-03 8:05 am
✔ 最佳答案
assume probability density function is continue,μ = 120
σ = 10.5
10% probability upper tail,
Φ inverse (90%, 120, 10.5) = 133.4562914
minimum candidate's score is 133.4562914 to qualify for admittance.
2009-03-03 8:00 am
1.645 is your key number here. This is because all scores at or above 1.645 standard deviations above any mean of a normal distribution will be in the top 10% of the population.
1.645(10.5) + 120 = 137.2725 and up
1.645(10.5) + 120 = 137.2725 and up
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