Math 210
Laboratory 8

In doing a project for a statistics class, a group of students wanted to see if there was a relationship between drinking coffee and smoking cigarettes.  The data found here, is simulated data based on the students findings.  Copy this data set into Minitab and answer the following questions.

1. Let’s first do some preliminary work to see if our data make sense and that their seems to be a representative sample of all Hope students.
   

1. What are the counts and proportions of males and females?  Does this seem reasonable for a random sample of Hope Students?  Why or why not?
   

• To do this, select Stat > Tables > Tally individual variables, then put ‘M/ F’ in the Variables: box and check both Counts and Percents.

2.  Make a pie chart for the percent of males and females.

•   To do this, select Graph > Pie Chart.  Make sure Chart raw data is chosen. In the  Categorical variables: box put ‘M/ F.’  Click on Labels to get your title on your graph and don't forget about slice labels.
  

3. What are the counts and proportions for each of the classes (F/So/J/Sr)?  Does this seem reasonable for a random sample of Hope students?  Why or why not?
   
4. Make a bar graph for the number of students in each class.

• To do this, select Graph > Bar Chart > Simple > OK.  In the box Categorical variables: select ‘F/So/J/Sr.’  Click on Bar Chart Options and click Decreasing Y and Click OK and then OK again.  Edit your bar chart appropriately.

5.  Run some descriptive statistics on each of the quantitative variables (Cups_Coffee/Day and Cigarettes/Day) and make histograms for them as well.  Stats > Basic Stats >Display Descriptive Statistics then click on Graphs and check the box Histogram of data.  Look at the values of the mean, standard deviation, the five number summaries, and the histograms.  You should find one data value that is not right.  A piece of data was entered incorrectly.  What is it?  How should you fix it?  Adjust this entry appropriately before going on to the next question. (You do NOT need to report the descriptive statistics or put the histograms in your report.)
   

2.  The students doing this survey were interested in whether there was an association between drinking coffee and smoking cigarettes.  They felt that if a student drank coffee, he or she would be more likely to smoke. 
   

1. To investigate their hypothesis, we need to create a two-way table from this data.  Using Coffee drinking Yes and Coffee Drinking No as to two row headings and Cigarette Smoking Yes and Cigarette Smoking No as the two Column Headings.  Each (of the four) cells in the table will contain a count.  Create the two-way table.    

• To do this click on Stat > Tables > Cross Tabulation and Chi-Square  in the box  For Rows: put in ‘Coffee(Y/N)’ and then For Columns:‘Smoke(Y/N)’  and click OK.  Copy your two way table into your Word document, edit it appropriately, and answer the following questions by using your table and dividing the appropriate counts.
  

2. What percent of all the students drink coffee?
3. What percent of all the students smoke?  
4. What percent of the students who drink coffee also smoke?
5. What percent of students who do not drink coffee smoke?
6. Based on these percents, do you think the student’s hypothesis that there is an association between smoking and coffee drinking is correct?  We will be able to answer this question more precisely after we study the sections on statistical tests, for now, just give your opinion on what the data show.

3. So far we have just investigated the relationship between coffee drinking and smoking categorically.  We will now do this quantitatively.  
   1. Find the means and standard deviations for the number of cigarettes smokers smoke based on whether or not they drink coffee.

• To do this click on Data > Copy > Columns to Columns.  In the Copy from columns: box put in ‘Coffee(Y/N)’ and ‘Cigarettes/Day’ in the Store Copied Data in Columns: box first choose in current worsheet, in columns, then in the box below this put in two free columns, say c8 and c9.  Click on the Subset the Data button and then click Specify which rows to include then click Rows that match then click on  Condition, and enter Smoke(Y/N) = “Y”  (you will need the quotes).  Click OK OK OK .This will select all the smokers and list whether or not they drink coffee in column 8 and the number of cigarettes they smoke in column 9.  Now find the mean and standard deviation for the new variable Cigarettes/Day_1 by the new variable Coffee(Y/N)_1.

2. Based on your means and standard deviations, do you think that coffee drinkers are more likely to smoke more?