Quiz3

The data set is from a case-control study of smoking and Alzheimer’s disease. The data set has two variables of main interest:

• smoking a factor with four levels “None”, “<10”, “10-20”, and “>20” (cigarettes per day)
• disease a factor with three levels “Alzheimer”, “Other dementias”, and “Other diagnoses”.

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Q1 Describe the largest group that has other dementias. Discuss it by number of cigarettes per day.

The largest group that has other dementias had no cigarettes per day.

Q2 Describe one group that has more cases than expected given independence (by chance). Discuss it by number of cigarettes per day.

The group that had more cases than expected was the group that had >20 cigarettes per day and had other dementias.

Q3 Does smoking seem to matter in determining other dementias? Discuss your reason using the masaic chart above.

It does not seem to matter when it comes to other dementias. The reason for this is because the largest group of people to get other dementias is did not smoke.

Q4 Create correlation plot for RailTrail.

Hint: The RailTrail data set is from the mosaicData package.

Q5 List all four variables that have negative correlation with the number of trail users (volume).

Spring, fall, cloudcover, and precipitation all have a negative correlation with the number of trail user.

Q6 What season seems to be least popular for trail users?

Fall seems to be the least popular season.

Q7 The correlation coefficient between hightemp and cloudcover is quite small. Would you be sure that the two variables are not related at all?

Hint: One word answer (e.g., yes or no) is NOT enough. Explain why. I think these two variables are related most of the time. Usually, when it is cloudy outside, the temperature goes down. With the exception of summer and humid, then cloud cover may not make much of a difference on the temperature. But, clouds will never cause hot weather.

Q7.a Continued from Q7. Create scatter plot. After examing the scatter plot, would you conclude that the two variables are not related at all?

Hint: Discuss your reason by explaining your scatter plot.

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Looking at the scatterplot, I would conclude that the two variables are actually not related.

Q8 Hide the messages, the code and its results on the webpage.

Hint: Use message, echo and results in the chunk options. Refer to the RMarkdown Reference Guide.

Q9 Display the title and your name correctly at the top of the webpage.

Q10 Use the correct slug.