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There is a normal distribution with EV 100 and SD 20. I take a random number, say 63 How to calculate EV of all values that follow the original distribution but excluding those bigger than 63?

In other words, assume there is a test where students score points with EV 100 and SD 20 (quite strange test where negative score is also possible ). To pass the test, students need to get at least 63 points. What is the average rate of students who didn't pass the test?

Mig
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  • See https://stats.stackexchange.com/questions/166273 and https://stats.stackexchange.com/questions/356023 inter alia. This site search turns up more. – whuber Apr 18 '22 at 18:51
  • If test scores are distributed normally with mean 100 and SD 20 then the proportion of students scoring 63 or lower is $0.0322$ or a little more than 3%. // How do I know that? How can you use printed normal CDF tables or software to find that? – BruceET Apr 18 '22 at 20:58

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