+-------------+-------------------+
| nlschools   | R Documentation   |
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Eighth-Grade Pupils in the Netherlands
--------------------------------------

Description
~~~~~~~~~~~

Snijders and Bosker (1999) use as a running example a study of 2287
eighth-grade pupils (aged about 11) in 132 classes in 131 schools in the
Netherlands. Only the variables used in our examples are supplied.

Usage
~~~~~

::

    nlschools

Format
~~~~~~

This data frame contains 2287 rows and the following columns:

``lang``
    language test score.

``IQ``
    verbal IQ.

``class``
    class ID.

``GS``
    class size: number of eighth-grade pupils recorded in the class
    (there may be others: see ``COMB``, and some may have been omitted
    with missing values).

``SES``
    social-economic status of pupil's family.

``COMB``
    were the pupils taught in a multi-grade class (``0/1``)? Classes
    which contained pupils from grades 7 and 8 are coded ``1``, but only
    eighth-graders were tested.

Source
~~~~~~

Snijders, T. A. B. and Bosker, R. J. (1999) *Multilevel Analysis. An
Introduction to Basic and Advanced Multilevel Modelling.* London: Sage.

References
~~~~~~~~~~

Venables, W. N. and Ripley, B. D. (2002) *Modern Applied Statistics with
S.* Fourth edition. Springer.

Examples
~~~~~~~~

::

    library(nlme)
    nl1 <- nlschools
    attach(nl1)
    classMeans <- tapply(IQ, class, mean)
    nl1$IQave <- classMeans[as.character(class)]
    nl1$IQ <- nl1$IQ - nl1$IQave
    detach()
    cen <- c("IQ", "IQave", "SES")
    nl1[cen] <- scale(nl1[cen], center = TRUE, scale = FALSE)

    nl.lme <- lme(lang ~ IQ*COMB + IQave + SES,
                  random = ~ IQ | class, data = nl1)
    summary(nl.lme)

