4.3 Two-way tables
Soccer is a unique in that one aspect is
...the purposeful use of the unprotected head for controlling and advancing the ball...
--- Gausche et al. (2000)
Some researchers suspect that repeatedly 'heading' the ball may impair brain function.
A study (Gausche et al. 2000) was conducted to determine
...whether long-term or chronic neuropsychological dysfunction (i.e. concussion) was present in collegiate soccer players
--- Gausche et al. (2000), p. 157.
Data were collected from 240 college students:
- The student type: One of 'soccer players' (63 students), 'non-soccer athletes' (96 students), or 'non-athletes' (81 students).
- The number of head concussions: Each student was asked about the number of head concussions they had experienced; 'zero' (158 students), 'one' (45 students), or 'two or more' (37 students) concussions.
Use the study data (Table 4.1) to answer the following questions.
| 0 | 1 | 2 or more | Total | |
|---|---|---|---|---|
| Soccer players | 45 | 5 | 13 | 63 |
| Non-soccer athletes | 68 | 25 | 3 | 96 |
| Non-athletes | 45 | 15 | 21 | 81 |
| Total | 158 | 45 | 37 | 240 |
- Compute the percentage of college students in the sample overall that have received exactly one concussion.
- Many possible graphs exists to display the data; four are shown in Fig. 4.2. What is the main message from each graph? Which graph do you think is best? Why?
FIGURE 4.2: Four different graphs displaying the soccer-data. 'S' mean a soccer player; 'NS' means a non-soccer athlete; 'NA' means a non-athlete
- Among the non-athletes, compute the odds of receiving two or more concussions. Interpret what this means.
- Among the soccer players, compute the odds of receiving two or more concussions. (Refer to Table 4.1.) Interpret what this means.
- Compute the odds ratio comparing the odds of a non-athlete player receiving two or more concussions to the odds of a soccer player receiving two or more concussions.
- Create a table of column percentages. What do these tell you?
- Create a table of row percentages. What do these tell you?
- Which one of these tables is probably more sensible, and why?
References
Gausche M, Lewis RJ, Stratton SJ, Haynes BE, Gunter CS, Goodrich SM, et al. Effect of out-of-hospital pediatric endotracheal intubation on survival and neurological outcome: A controlled clinical trial. Journal of the American Medical Association. 2000;283(6):783–90.