It is also shown that the minimum bubble attrition velocity is far larger than the minimum fluidizing velocity because energy is required to produce attrition.
For fine powders, two surface modification approaches for producing dispersible powders are considered: first, suitable for powders >10 μm where attrition is minimum, and second, suitable for finer particles including inhalable (2 5 μm), where simultaneous micronization and surface modification is performed.
Allowing for 10% attrition, the minimum total sample size was 411 children.
In spite of these obstacles we did manage to recruit sufficient participants into the trial and to keep attrition to a minimum.
Based on a clinically meaningful difference for the primary outcome measure of 9 points, and allowing for a 10% attrition rate, a minimum number of 60 subjects will be required for each treatment group (assuming 80% power and a 0.05 alpha value).
Norman & Streiner [ 90] recommend 5 participants for each independent variable included in a regression model; therefore, since the study included twenty independent confounding variables, and taking into account a possible 20% attrition rate, the minimum sample size was calculated as follows: 105 + (5 × 20) = 205 plus 20% = 246.
To keep the attrition rates at a minimum, all adolescents absent at a given measurement will be provided another possibility in the same time period to complete the questionnaire.
The required minimum sample size after allowing for 20% attrition at 95% confidence interval was 380.
With a 2 1 randomization, a power of 80% at minimum, and accounting for patient and data attrition of up to 40%, the required number of patients to receive the Boston Scientific VNS system has been estimated to be 96 patients.
It is expected that an initial sample of 40 will result in a final sample of at least 30, allowing for attrition over the study period (minimum of 150 from across five communities).
