Let x be normally distributed with mean µ = 25 and standard deviation σ = 5. find the value x such that p(x ≥ x) = 0.1736

Respuesta :

The value x of interest is also the value that makes the probability of interest be
  p(X ≤ x) = 1 - 0.1736. That value of x is determined by a suitable calculator to be about 29.7.
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Answer:

The score is X = 29.7.

Step-by-step explanation:

Problems of normally distributed samples can be solved using the z-score formula.

In a set with mean [tex]\mu[/tex] and standard deviation [tex]\sigma[/tex], the zscore of a measure X is given by:

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

The Z-score 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. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.

In this problem, we have that:

[tex]\mu = 25, \sigma = 5[/tex]

Find the value x such that p(x ≥ x) = 0.1736.

This is X when Z has a pvalue of 1-0.1736 = 0.8264. So it is X when Z = 0.94. So

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

[tex]0.94 = \frac{X - 25}{5}[/tex]

[tex]X - 25 = 5*0.94[/tex]

[tex]X = 29.7[/tex]

The score is X = 29.7.