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The playing time X of classical CDs has the normal distribution with mean 54 and standard
deviation 5; the N(54, 5) distribution. What is the relative frequency of classical CDs with playing
time X between 49 and 69 minutes?


Sagot :

Using the normal distribution, it is found that the relative frequency of classical CDs with playing time X between 49 and 69 minutes is 0.8403 = 84.03%.

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.

The mean and the standard deviation are given, respectively, by:

[tex]\mu = 54, \sigma = 5[/tex]

The relative frequency of classical CDs with playing time X between 49 and 69 minutes is the p-value of Z when X = 69 subtracted by the p-value of Z when X = 49, hence:

X = 69:

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

[tex]Z = \frac{69 - 54}{5}[/tex]

Z = 3

Z = 3 has a p-value of 0.9987.

X = 49:

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

[tex]Z = \frac{49 - 54}{5}[/tex]

Z = -1

Z = -1 has a p-value of 0.1584.

0.9987 - 0.1584 = 0.8403.

More can be learned about the normal distribution at https://brainly.com/question/4079902

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