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 group that does not smoke at all.

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 smokes at least 20 or more ciggaretts a day.

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

Yes, because it has the highest amount of correlations.

Q4 Create correlation plot for RailTrail.

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

##            hightemp lowtemp avgtemp spring summer  fall cloudcover precip
## hightemp       1.00    0.66    0.92  -0.33   0.67 -0.40      -0.10   0.13
## lowtemp        0.66    1.00    0.90  -0.39   0.74 -0.41       0.37   0.37
## avgtemp        0.92    0.90    1.00  -0.39   0.77 -0.44       0.14   0.27
## spring        -0.33   -0.39   -0.39   1.00  -0.74 -0.47      -0.10  -0.25
## summer         0.67    0.74    0.77  -0.74   1.00 -0.24       0.17   0.34
## fall          -0.40   -0.41   -0.44  -0.47  -0.24  1.00      -0.08  -0.09
## cloudcover    -0.10    0.37    0.14  -0.10   0.17 -0.08       1.00   0.37
## precip         0.13    0.37    0.27  -0.25   0.34 -0.09       0.37   1.00
## volume         0.58    0.18    0.43  -0.04   0.23 -0.25      -0.37  -0.23
##            volume
## hightemp     0.58
## lowtemp      0.18
## avgtemp      0.43
## spring      -0.04
## summer       0.23
## fall        -0.25
## cloudcover  -0.37
## precip      -0.23
## volume       1.00

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

Fall, cloudcover, precip, spring.

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

Autom is the least popular season for the RailTrail.

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.

We can not be sure that the two variables of hightemp and cloudcover are not related at all to each other. However there could be a different nonlinear correlation between the two variables.

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.