- CFA Exams
- CFA Level I Exam
- Study Session 3. Quantitative Methods (2)
- Reading 11. Hypothesis Testing
- Subject 8. Hypothesis Tests Concerning the Mean: T-Test vs. Z-Test

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**CFA Practice Question**

The manufacturer of a sore throat spray claims that the product brings pain relief to sore throat sufferers within 5 seconds of contact. The manufacturer reported that for a random sample of 100 sore throat sufferers, the mean time of relief was 3.2 seconds with a standard deviation of 1 second. Find the rejection region for the test if testing at z < z

_{0.01}.A. z < z

_{0.01}= -2.33B. z < z

_{0.01}= -1.96C. t < t

_{0.01}= -3.18###
**User Contributed Comments**
8

User |
Comment |
---|---|

danlan |
How to get this? |

hizmo |
Look at the z table. |

julamo |
Do we really need to know those z-table values by heart??? Doesn't make any sense |

Xocrevilo |
A reference page I use for practice questions. The same values keep on preparing, thus eventually you should hardly need to refer to it at all: http://www.stat.tamu.edu/stat30x/zttables.html |

mishis |
I thought this meant that Alpha was 2% so .9800 in Z table is 2.06. Anyone? |

Mariecfa |
This is a left tailed test. Look at the Z Table: Negative Values for the area .01 to find the Z Value which is -2.33. Also if you know that the area (0.01) which is to the left of the test statistic Z, you can subtract that value of 0.01 to get a 99% Confidence Interval that would give you -2.33 for the Z Value on the left tail from remembering the common 99% Confidence Interval is 2.33 for the Z Value. You would not have to look at a Z table. |

bhaynes |
It is key that you memorize these values for a one-sided z-test..... 99% - 2.33 95% - 1.645 90% - 1.28 For two sided: 99% - 2.58 95% - 1.96 90% - 1.645 |

zzhumanov |
thank you Bhaynes |