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A normal distribution has \mu = 65 and \sigma = 10. Find the probability that the average score of a group of n = 4 people is between 70 and 75 (both limits included).

Sagot :

Answer:

The probability that the average score of a group of n = 4 people is between 70 and 75=0.13591

Step-by-step explanation:

We are given that

[tex]\mu=65[/tex]

[tex]\sigma=10[/tex]

n=4

We have to find the probability that the average score of a group of n = 4 people is between 70 and 75.

[tex]P(70<\bar{x}<75)=P(\frac{70-65}{\frac{10}{\sqrt{4}}}<\frac{\bar{x}-\mu}{\frac{\sigma}{\sqrt{n}}}<\frac{75-65}{\frac{10}{\sqrt{4}}})[/tex]

[tex]=P(\frac{5}{5}<Z<\frac{10}{5})[/tex]

[tex]=P(1<Z<2)[/tex]

[tex]=P(Z<2)-P(Z<1)[/tex]

[tex]=0.97725-0.84134[/tex]

[tex]=0.13591[/tex]

Hence,  the probability that the average score of a group of n = 4 people is between 70 and 75=0.13591