It has been proposed that the size of the ventricle, a physiological feature of the brain as measured by X-rays, may be associated with abnormal EEG (brain wave)

readings. Table 13.15 shows ventricle (V) sizes and results of EEG readings (E, coded 0 for normal and 1 for abnormal) for a set of 71 elderly patients.

(a) Subdivide the data set into five subgroups based on ventricle size. Within each subgroup, calculate the ln(odds) of an abnormal EEG. Plot the ln(odds) versus the midpoint of the ventricle class. Does a logistic model appear appropriate?
Hint: Remember that we often add 1 to the counts in all categories to avoid undefined ln(odds) when sample sizes are small.

(b) Fit a logistic model and interpret the results.

Transcribed Image Text:

Table 13.15 Data on EEG for Exercise 3. VE V E V E > E V E V E 53 0 37 0 56 0 59 0 58 63 0 25 0 60 0 58 0 50 0 58 1 70 0 68 1 50 0 59 0 51 0 76 0 74 1 62 1 41 0 65 0 50 0 94 1 73 1 72 0 45 1 56 0 56 0 75 0 76 0 78 1 50 0 68 0 47 0 66 0 42 1 76 1 57 0 65 0 51 0 83 1 51 0 80 1 70 0 68 49 0 56 1 58 1 58 1 64 1 60 1 57 0 54 0 58 0 63 1 61 0 70 57 1 84 50 48 BRO 0 40 0 51 1 58 1 70 0 58 0 67 35 51 1 57 0 85 1 62 0 65 0