I'm wondering if a treatment has an effect on my mite population. Therefore I've got a dataset with repeated measurements, some data is missing. data: <br> <pre> <b>ID Treatment Mites Time Location StartPopulation otherFactor</b> ID1 Control 7 1 Loc1 5 10000 ID1 Control 8 2 Loc1 5 10000 ID1 Control 10 3 Loc1 5 10000 ID2 Control 12 1 Loc2 11 13000 ID2 Control 2 Loc2 11 13000 ID2 Control 14 3 Loc2 11 13000 ID3 Treatment 20 1 Loc1 20 12000 ID3 Treatment 22 2 Loc1 20 12000 ID3 Treatment 3 Loc1 20 12000 and so on.. totally: 110<em>ID</em>s; 7 different measurement <em>Time</em>stamps </pre> variables: <pre> ID: factor, unique ID for each population Treatment: factor ("Treatment" or "Control") Mites: numeric, the variable I'm interested in Time: factor with total 7 levels Location: factor with total 11 levels StartPopulation: numeric (mean of Mites for t=-3, -2, -1 -> before Treatment started) otherFactor: numeric </pre> I'm interested if my <em>Treatment</em> changed the <em>Mites</em> count - and if yes if there's an increase in it's effect over time. <em>StartPopulation</em> sure had an influence on <em>Mites</em>, <em>otherFactor</em> and <em>Location</em> could've had also. As I use a mixed model I'd like to use <b>lmer in R</b>. My syntax looks anything like that: <code> PPP <- lmer(Mites ~ Treatment + StartPopulation + Location + otherFactor + (1|Time) + (1|ID), data=vat_database) </code> But as I don't really know what I typed exactly I'm glad if you can help me understanding how this works. Thank you so much, kind regards