# What model to use for a 'spraying experiment'?

I separate my plants into four groups of 16, and I spray them to keep the bugs away:

group 1: I spray daily
group 2: I spray every 2 days
group 3: I spray every 3 days
group 4: I spray every 4 days


at the end of the 12 days, I check number of plants that's bug free

group 1 is: 12
group 2 is: 10
group 3 is: 7
group 4 is: 6


How should I fit a model to this?

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We need informative title, so I updated yours; feel free to choose another one. It looks like you're after some kind of a dose-response relationship (with counts or % as an outcome). –  chl Dec 19 '11 at 8:53