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. Author manuscript; available in PMC: 2016 Jan 1.
Published in final edited form as: Addict Behav. 2014 Aug 7;40:16–20. doi: 10.1016/j.addbeh.2014.07.030

Table 1.

Parameter Estimates from the GEE Model of Home Practice (in Hours)

Variable IRR SE z p
Centered linear time 10.62 3.30 7.61 <.001
Centered quadratic time .53 .05 −6.51 <.001

Notes. IRR = incident rate ratio. SE = Semi-robust standard error. z = z-score for the parameter.