Friday, February 24, 2006

Re: st: Re: simple way to create missing data that is "missing at random" from a small datset

Suzy: You wanted to create missingness according the to a MAR process, in your case the probability of missingness in the variable bmi should depend on the variable age. So we created the probability of missingness for each observation. The youngest person in your dataset has a probablity of missingness of invlogit(-8 + .1*28) = .0054863 (type -di invlogit(-8 + .1*28)-) and the oldest person has a missingness of invlogit(-8 + .1*82) = .549834. If the probability of missingness was constant (or random and unrelated to any of the other variables) than the missingness mechanism would be missing completely at random MCAR.

HTH, Maarten

--- Suzy <> wrote: > I'm not sure what the implications are of the std dev and the > max values of p (.549).

----------------------------------------- between 1/2/2006 and 31/3/2006 I will be visiting the UCLA, during this time the best way to reach me is by email

Maarten L. Buis Department of Social Research Methodology Vrije Universiteit Amsterdam Boelelaan 1081 1081 HV Amsterdam The Netherlands

visiting adress: Buitenveldertselaan 3 (Metropolitan), room Z214

+31 20 5986715 -----------------------------------------

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