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Assignment Stats 250 W11 HW 2 Graded Point Total: 27.5 out of 30 1.5 out of 2.5 points Feedback: "Prove" is too strong a word. Need to discuss outlier and provide your name. Required Assignment Stats 250 W11 HW 2 Question 1 (Chapter 2) The dataset pennstate1.sav (download HERE ) contains survey responses for 190 college students. One question was "How many hours did you sleep last night"? The histogram is provided to the right. Produce a qq plot of the hrssleep data (upload your JPEG, JPG, GIF, or PNG plot file below, including a title). Comment on whether a normal distribution is reasonable as a model for this variable. Explain what features of each plot lead you to your answer. 4/17/2011 www.lecturebook.com/homeworks/sho… lecturebook.com/homeworks/show/35 1/11

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Your Answer: A normal distribution is reasonable as a model for this variable. First of all, the histogram is approximately symmetric and bell shaped. The qq plot also further proves it is a normal distribution due to the fact that it is a roughly straight line with a positive slope and most of the points follow the given line. So yes, a normal distribution is very reasonable. Solution: With the exception of one large outlier, the shape of the histogram is close to a normal (bell-shaped) model. On the qq plot, most points fall along a straight line with a positive slope and the outlier is also visible on this plot. Therefore, apart from this outlier (which should be investigated further), a normal distribution is reasonable as a model for the hours of sleep for the population of college students represented by this sample. 4/17/2011 www.lecturebook.com/homeworks/sho… lecturebook.com/homeworks/show/35 2/11
a. 0.5 out of 0.5 points Is the type of study described above an observational study or an experiment? 1. Observational study 2. Experiment Solution: 2. Experiment b. Did blinding play a role in this study? (yes, no, or can’t tell) 1 Yes Question 2 (Chapter 4) Protection from the Flu – A study seeks to compare the effectiveness of two types of respiratory protection during influenza outbreaks. A total of 440 nurses who were caring for patients with the flu were randomly divided into two groups. The 240 nurses assigned to Group 1 received surgical masks to wear while caring for their flu patients, and the remaining 200 nurses received fitted N95 respirators to wear while caring for their flu patients. The researcher who evaluated the nurses over the study period (to assess whether or not the nurse got influenza) did not know which respiratory protection each nurse actually wore when treating their flu patients. The table below summarizes some of the study results. Use these results to answer the following questions. Influenza Status Group Yes, got influenza No, did not get influenza Total Group 1 (Surgical Mask) 72 168 240 Group 2 (N95 Respiratory) 38 162 200 Total 110 330 440 4/17/2011 www.lecturebook.com/homeworks/sho… lecturebook.com/homeworks/show/35 3/11

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0.5 out of 0.5 points 1.
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## 2 - 4/17/2011 www.lecturebook.com/homeworks/sho Assignm ent...

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