The reading speed of sixth-grade students is approximately normal, with a mean speed of 125 words per minute and a standard deviation of 24 words per minute. What is the probability that a randomly selected sixth-grade student reads less than 100 words per minute?

Respuesta :

Answer:

0.148783124

Step-by-step explanation:

the probability that a randomly selected sixth-grade student reads less than 100 words per minute

P(X < 100)

= P(z < (100 - 125)/24))

= P(z < -1.0417)                                (from the z-table)

= 0.148783124

The probability that a randomly selected sixth-grade student reads less than 100 words per minute is 0.1492.

What is a Z-table?

A z-table also known as the standard normal distribution table, helps us to know the percentage of values that are below (or to the left of the Distribution) a z-score in the standard normal distribution.

As it is given that the distribution is normal, with a mean of 125 words, while the standard deviation is 24 words. Therefore, the probability that a randomly selected sixth-grade student reads less than 100 words per minute can be written as,

[tex]P(X < 100)=P(z < \dfrac{100-\mu}{\sigma})[/tex]

                   [tex]=P(z < \dfrac{100-\mu}{\sigma})\\\\=P(z < \dfrac{100-125}{24})\\\\=P(z < -1.0416)\\\\=0.1492[/tex]

Hence, the probability that a randomly selected sixth-grade student reads less than 100 words per minute is 0.1492.

Learn more about Z-table:

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