Question

For
Questions 6 - 8, let the random variable X follow a Normal
distribution with variance σ^{2} = 625. |

Q6. A random sample of n = 50 is obtained with a sample mean, X-Bar of 180. |

What is the probability that population mean μ is greater than 190? |

a. What is Z-Score for μ greater than 190 ==> |

b. P[Z > Z-Score] ==> |

Q7. What is the probability that μ is between 198 and 211? |

a. What is Z-Score1 for μ greater than 198 ==> |

b. What is Z-Score2 for μ less than 211 ==> |

c. P[Z-Score1 < Z < Z-Score2] ==> |

Q8. A second random sample of n = 75 is obtained, again with a sample mean X-Bar of 180. What is the probability that μ is between 177 and 190? |

a. What is Z-Score1 for μ greater than 177 ==> |

b. What is Z-Score2 for μ less than 190 ==> |

c. P[Z-Score1 < Z < Z-Score2] ==> |

Answer #1

6)

a)

mean = 180 . s = 625 , n =50

P(x > 190) = P(z > (190 -180)/(625/sqrt(50))

= P(z > 0.1131)

= 0.4550

7)

a)

P(z> 198) = P(z >(198 - 180)/(625/sqrt(50))

= 0.2036

P(x< 211) = P( z < (211 - 180)/(625/sqrt(50))

= 0.3507

P(198 < x < 211)

= P((198 - 180)/(625/sqrt(50)) < z < (211 -
180)/(625/sqrt(50))

= P(0.2036 < z < 0.3507)

= 0.0564

8)

n = 75

P(177 < x <190)

P(z> 177) = P(z >(177- 180)/(625/sqrt(50))

= -0.0339

P(x< 190) = P( z < (190 - 180)/(625/sqrt(50))

= 0.1131

P(- 0.0339 < z < 0.1131)

= 0.0585

Let the random variable X follow a Normal distribution with
variance σ2 = 625.
A random sample of n = 50 is obtained with a sample mean, X-Bar
of 180.
What is the probability that μ is between 198 and 211?
What is Z-Score1 for μ greater than 198?

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