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The scores on a standardized exam are normally distributed with a mean of 400 and a standard deviation of 50.

Approximately 40% of the scores are greater than which score?

370

387

413

430


Sagot :

Using the normal distribution, it is found that approximately 40% of the scores are greater than 413.

Normal Probability Distribution

The z-score of a measure X of a normally distributed variable with mean [tex]\mu[/tex] and standard deviation [tex]\sigma[/tex] is given by:

[tex]Z = \frac{X - \mu}{\sigma}[/tex]

  • The z-score measures how many standard deviations the measure is above or below the mean.
  • Looking at the z-score table, the p-value associated with this z-score is found, which is the percentile of X.

In this problem, we have that the mean and the standard deviation of the scores are given by:

[tex]\mu = 400, \sigma = 50[/tex]

Approximately 40% of the scores are greater than the 60th percentile, which is X when Z = 0.253.

Then:

[tex]Z = \frac{X - \mu}{\sigma}[/tex]

[tex]0.253 = \frac{X - 400}{50}[/tex]

X - 400 = 50(0.253)

X = 412.65.

Rounding up, approximately 40% of the scores are greater than 413.

More can be learned about the normal distribution at https://brainly.com/question/24663213

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