In Bluefin, you can define cohort attributes to control how the participants are generated. There are three kinds of attributes: age range, body surface area, and weight. Each cohort can have a different set of attributes, so if you want to vary the weight for certain treatment arms, you can do that by creating multiple cohorts.
Once you've added an attribute, you have controls. Distributions can be defined as "normal" or "uniform" - normal being a bell-shaped distribution, and uniform being an even distribution across the range. Below, we have a uniform distribution between 1 and 65 years old, meaning participants entering with this cohort will have ages generated according to that attribute.
