Yes/No Formula

Don't know much about the formula aspect in families, but I have read and printed many posts about it and will start learning. But for now I have a quick question about yes/no formula's. In the family I am creating there are High profiles (HP) and Low profiles (LP). I am using a yes/no parameter that I would like a formula to read off where (HP) is check then my height is 11" and if my (LP) is check my height will be 8". I know its probably a simple formula but I have no idea on how to start. I thought about building a type catalog but it would be too large and everything is dependent on the CFM of this family so it would be really hard to organize. So instead I'm letting the guys just check a box if it is (HP) or (LP) and let them determine the sizes they need. Thanks!

Im assuming you have the yes/no parameters on your HP and LP parameters. Where i would go with the height parameter is "if(HP, 11'', if (LP, 8'',(some nominal value)))", or "if( HP, 11'',8'')". Another, thing i would do i set the LP parameter to be triggered if HP is not selected. A simple "not(HP)" will protect you from having both or neither option triggered.