The mean score on a certain standardized test is 500, with a standard deviation on 75. Jessie scored in the 75th percentile. What was Jessie's score and the z score?
Please help as soon as possibel. thx
mean score 500, standard dev. 75, score in 75th percentile
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stapel_eliz
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FWT wrote:The mean score on a certain standardized test is 500, with a standard deviation on 75. Jessie scored in the 75th percentile. What was Jessie's score and the z score?
They should have given you some sort of formula for converting between z-score and the mean "mu" and standard deviation "sigma".
. . . . .
In your case, you have:
. . . . .
A score in the 75th percentile represents a score which is greater than 75% of all of the scores. With respect to the standard-normal curve, it represents the probability that a given score Z will be in the lower 75% of the scores: P(Z < z) = 0.75. Depending on the table (or calculator) you're using, this value will be something close to 0.674. Then:
. . . . .
Solve this for Jessie's score X.
Hope that helps!
Re: mean score 500, standard dev. 75, score in 75th percentile
thanks i got it