Adjusting intensity of groups of lights

Hey all,

I have a file attached with 2 groups of lights. The ability to group lights is great, but I’m trying to adjust the intensity of the entire group and having trouble doing so. I have a feeling it’s something really obvious but don’t see it. Right now I have to go in to the intensity box of each light and change it – which as you can imagine is quite time consuming. Can anyone tell me whether this is possible?

Thank you.Lights.3dm (113.0 KB)