Preface to First Edition - lib

METHODS FOR NON-NORMAL DISTRIBUTIONS 233Table 13.2:epilepsy data (continued).treatment base age seizure.rate period subjectplacebo 6 25 5 4 3placebo 8 36 4 1 4placebo 8 36 4 2 4placebo 8 36 1 3 4placebo 8 36 4 4 4placebo 66 22 7 1 5placebo 66 22 18 2 5placebo 66 22 9 3 5placebo 66 22 21 4 5placebo 27 29 5 1 6placebo 27 29 2 2 6placebo 27 29 8 3 6placebo 27 29 7 4 6placebo 12 31 6 1 7placebo 12 31 4 2 7placebo 12 31 0 3 7placebo 12 31 2 4 7......In a clinical trial reported by Thall and Vail (1990), 59 patients with epilepsywere randomised to groups receiving either the antiepileptic drug Progabideor a placebo in addition to standard chemotherapy. The numbers of seizuressuffered in each of four, two-week periods were recorded for each patient alongwith a baseline seizure count for the 8 weeks prior to being randomised totreatment and age. The main question of interest is whether taking Progabidereduced the number of epileptic seizures compared with placebo. A subset ofthe data is given in Table 13.2.Note that the two data sets are shown in their ‘long form’ i.e., one measurementper row in the corresponding data.frames.13.2 Methods for Non-normal DistributionsThe data sets respiratory and epilepsy arise from longitudinal clinical trials,the same type of study that was the subject of consideration in Chapter 12.But in each case the repeatedly measured response variable is clearly not normallydistributed making the models considered in the previous chapter unsuitable.In Table 13.1 we have a binary response observed on four occasions,and in Table 13.2 a count response also observed on four occasions. If wechoose to ignore the repeated measurements aspects of the two data sets wecould use the methods of Chapter 7 applied to the data arranged in the ‘long’© 2010 by Taylor and Francis Group, LLC