[SPLIT] test score was in top 20%: z-score is at least...?  TOPIC_SOLVED

Standard deviation, mean, variance, z-scores, t-tests, etc.

[SPLIT] test score was in top 20%: z-score is at least...?

Postby ivonagui on Mon Jun 15, 2009 6:39 pm

a person received a test score that was in the top 20% of everyone who has taken the test. the test scores are normally distributed. this perosn's Z score must be at least what/
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Postby stapel_eliz on Mon Jun 15, 2009 7:03 pm

Use your table of z-scores. The top 20% will be the bottom 50%, plus another 30%, so find the z-score corresponding to 0.3000, or as close as you can get. You should arrive at a value in the vicinity of 0.8415. :wink:
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