Statistics for Social Sciences
Correlation
This assignment was designed to help students 1) develop a deeper understanding of the purposes of correlational techniques and 2) become more familiar with hand-computed and computer-based correlational analyses.
Use the smoking data provided to complete the following steps. NOTE: you can copy and paste the data into SPSS if you use the electronic word file of this assignment I have sent. Show all your computational work.
Hand compute the correlation between the number of years smoking (YR.SMOKE) and the number of cigarettes smoked per day (CIG.DAY).
Hand calculate the correlation between the number of cigarettes smoked per day and the level of carbon monoxide expired (CO.LEVEL).
Report both correlation coefficients and describe the strength and direction of each in words (based on Tables 5.1 and 5.2 in text).
d. Calculate the coefficients of determination and alienation for both correlations and explain what the numbers mean.
e. Draw two Venn-like diagrams similar to those in Figure 5.5 (p. 90) to demonstrate the coefficient of determination for both correlations. Be sure to label them using the variable names provided (ie, CIG.DAY, YR.SMOKE, and CO.LEVEL).
f. Draw a scatterplot to illustrate the relationship between CIG.DAY and CO.LEVEL. Describe the slope of the scatterplot.
g. Is it correct to say that higher intake of cigarettes (CIG.DAY) causes higher levels of carbon monoxide (CO.LEVEL)? Based solely on your correlation coefficient, explain why or why not.
2. Use the same data and compute the following using SPSS. Be sure to enter the data accurately into the program and to print off copies of your data and output files.
a. Determine the two Pearson correlation coefficients for the data provided below.
b. If you haven't already, analyze (using correlation ( bivariate) all three variables at once so that you see a correlation matrix in your printout.
c. Have SPSS generate three scatterplots: CIG.DAY and YR.SMOKE, CIG.DAY and CO.LEVEL, and YR.SMOKE and CO.LEVEL.
SEX
YR.SMOKE
CIG.DAY
CO.LEVEL
Female
20
15
17
Male
27
40
28
Female
14
28
40
Female
20
12
15
Female
10
40
33
Male
30
25
29
Female
35
33
29
Female
50
10
13
Female
15
20
30
Female
