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The grades of a science test are normally distributed. Thanh finds that his grade on the test has a z-score of â€""2. 5. Which statement must be true? Thanh’s grade is 2. 5 standard deviations below the mean of the test grades. Thanh’s grade is 2. 5 points below the mean of the test grades. Thanh’s grade is 2. 5 standard deviations above the mean of the test grades. Thanh’s grade is 2. 5 points above the mean of the test grades.

Respuesta :

Using the normal distribution, it is found that the correct option is:

  • Thanh grade is 2.5 standard deviations above the mean of the test grades.

In a normal distribution with mean [tex]\mu[/tex] and standard deviation [tex]\sigma[/tex], the z-score of a measure X is given by:

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

  • It measures how many standard deviations the measure is from the mean.  
  • After finding the z-score, we look at the z-score table and find the p-value associated with this z-score, which is the percentile of X.

In this problem, Tnanh grade has Z = 2.5, hence, it is 2.5 standard deviations above the mean of the test grades.

To learn more about the normal distribution, you can take a look a https://brainly.com/question/24663213

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