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”.

##                 smoking None <10 10-20 >20
## disease                                   
## Alzheimer                126  15    30  27
## Other dementias           79   8    33  44
## Other diagnoses          104   5    47  20

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

The largest group that has other dementias smokes 0 cigarettes a day.

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

There were more cases than expected in other dementias where the person smokes more than 20 cigarettes per day.

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

I believe that smoking is more of a confounding variable and the correlation is based off of other sets of variables as the spread of cases in all of the diseases has a similar pattern with cigarettes per day.

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, cloudcover, fall, and precipitation all have negative correlation with the number of trail users (volume).

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

The least popular season for trailusers is fall, at -0.25 correlation.

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.

No, can not be sure. Correlation coefficient only gives us info on linear relationships, not non-linear relationships.

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.

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.