# Stat 200 Exam 2

Pages: 19 (5054 words) Published: November 11, 2012
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Points Awarded| 34.00|
Points Missed| 6.00|
Percentage| 85.0%|

1.
The level of significance associated with a significance test is the probability A) of rejecting a true null hypothesis.
B) of not rejecting a true null hypothesis.
C) that the null hypothesis is true.
D) that the alternative hypothesis is true.

Feedback: This level of significance, commonly set to α equal to 0.05, is used to set the cut-off as the maximum probability a researcher would use in order to reject a true null hypothesis. Points Earned:| 1.0/1.0| |

2.
A null hypothesis is that the average pulse rate of adults is 70. For a sample of 64 adults, the average pulse rate is 71.8. A significance test is done and the p-value is 0.02. What is the most appropriate conclusion based on α of 0.05? A) Conclude that the population average pulse rate is 70.  B) Conclude that the population average pulse rate is 71.8.  C) Reject the hypothesis that the population average pulse rate is 70.  D) Reject the hypothesis that the sample average pulse rate is 70.

Feedback: Since the p-value is less than α we would reject the Ho the null hypothesis that the population average pulse rate is 70. Points Earned:| 1.0/1.0| |

3.
If the result of a hypothesis test for a proportion is statistically significant, then A) the null hypothesis is rejected.
B) the alternative hypothesis is rejected.
C) the population proportion must equal the null value.

Feedback: When a hypothesis test is statistically significant then we reject Ho the null hypothesis Points Earned:| 1.0/1.0| |

4.
Which of the following conclusions is not equivalent to rejecting the null hypothesis? A) The results are statistically significant.
B) The results are not statistically significant.
C) The alternative hypothesis is accepted.
D) The p-value < α (the significance level)

Feedback: All are equivalent conclusions for rejecting Ho except when results are not statistically significant (i.e. we do not reject Ho) Points Earned:| 1.0/1.0| |

5.
Determine if the statement is a typical null hypothesis (Ho) or alternative hypothesis (Ha). There is no difference between the proportion of overweight men and overweight women in America. A) Null hypothesis

B) Alternative hypothesis

Feedback: Ho refers to no difference or change or equal to. Ha will be the research hypothesis that involves either a difference, greater than, or less than. Points Earned:| 1.0/1.0| |

6.
A safety officer wants to prove that μ = the average speed of cars driven by a school is less than 25 mph. Suppose that a random sample of 14 cars shows an average speed of 24.0 mph, with a sample standard deviation of 2.2 mph. Assume that the speeds of cars are normally distributed. What are the appropriate null and alternative hypotheses? A) Ho: μ = 25 and Ha: μ < 25

B) Ho: μ = 25 and Ha: μ > 25
C) Ho: μ = 25 and Ha: μ ≠ 25
D) Ho: μ ≠ 25 and Ha: μ = 25
E) Ho: x-bar = 24 and Ha: x-bar < 24
F) Ho: x-bar = 24 and Ha: x-bar > 24
G) Ho: x-bar = 24 and Ha: x-bar ≠ 24
H) Ho: x-bar ≠ 24 and Ha: x-bar = 24

Feedback: The word less is the key term in determining the correct Ha expression. Exceeds implies that the investigator is only interested in whether the true population mean is less than 25. The value of 24 is the sample mean. Points Earned:| 1.0/1.0| |

7.
An ESP experiment is done in which a participant guesses which of 4 cards the researcher has randomly picked, where each card is equally likely. This is repeated for 200 trials. The null hypothesis is that the subject is guessing, while the alternative is that the subject has ESP and can guess at higher than the chance rate. The subject actually...

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