Example Balaams design

This is a well-known example initially described by Hunter et al. (1970). The aim was to determine the effect of amantadine (treatment A) on subjects suffering from Table 7.7 Average scores for amantadine trial. Table 7.7 Average scores for amantadine trial. Parkinsonism. The trial was placebo controlled (treatment B). After a run-in period of one week during which baseline information was recorded, there were two four-weekly treatment periods, without a washout period. Weekly scores (0-4) were...

Example fourway crossover trial

We will consider the four-way cross-over trial analysed in Section 7.4 which compared the effects of three drugs A, C and D and a placebo B on blood flow. This time, no values are set to missing and therefore the study is more balanced (across random effects). Each treatment period lasted a week and was followed by a washout period also lasting a week. An analysis fitting a random effects model (i.e. a compound symmetry pattern) is compared with analyses fitting general covariance matrices. The...

Sas code for cubic model selected

MODEL virus age type month month2 month3 S DDFM KR RANDOM INT month month2 SUB pat TYPE UN UN 1,1 , UN 2,2 and UN 3,3 are the variance component estimates for the patient, patient-time and patient-time2 random coefficients. UN 2,1 , UN 3,1 and UN 3,2 are the covariances between the random coefficients. Note that the relative sizes of the patient-time and patient-time2 variance components cannot be compared directly with other variance components because they involve time. AICC smaller is better...

Example ABBA crossover design

We illustrate the AB BA cross-over design with results from an unpublished study comparing two diuretics in the treatment of mild to moderate heart failure. After initial screening for suitability, there was a period of not less than one day, and not more than seven days, where diuretic treatment was withheld. Immediately prior to randomisation to either the AB sequence of treatment, or the BA sequence, baseline observations were taken. Each treatment period lasted for five days, with an...

Repeated Measures Data

There were four post-treatment visits in the multi-centre hypertension trial introduced in the previous section. However, so far in this chapter we have chosen only to model measurements made at the final visit, which were of primary interest. An alternative strategy would be to include measurements from all four post-treatment visits in the model. Since measurements are made repeatedly on the same patients, we can describe these types of data as repeated measures data. For illustrative...

Some Useful Definitions

We conclude this introductory chapter with some definitions. The terms we are introducing here will recur frequently within subsequent chapters, and the understanding of these definitions and their relevance should increase as their applications are seen in greater detail. The terms we will introduce are containment, balance and error strata. In the analyses we will be presenting, we usually wish to concentrate on estimates of treatment effects. With the help of the definitions we are...