Variables:
A data frame with 400 randomly subsampled observations on the following 8 variables.
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ppvtr.36
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a numeric vector with data on the Peabody Picture Vocabulary Test (Revised) administered at 36 months
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first
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indicator for whether child was first-born
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b.marr
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indicator for whether mother was married when child was born
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income
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a numeric vector with data on family income in year after the child was born
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momage
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a numeric vector with data on the age of the mother when the child was born
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momed
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educational status of mother when child was born (1 = less than high school, 2 = high school graduate, 3 = some college, 4 = college graduate)
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momrace
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race of mother (1 = black, 2 = Hispanic, 3 = white)
Note that momed would typically be an ordered factor while momrace would typically be an unorderd factor but both are numeric in this data.frame in order to illustrate the mechanism to change the type of a missing_variable