[R] linear model: Test difference between coefficients and given values (t.test?)

Katharina May may.katharina at googlemail.com
Sat Aug 8 22:15:48 CEST 2009

Thanks to somebody I got the hint to use offset for the purpose of
validating if there's
a difference between the intercept and slope of a model and some
provided values for
the coefficients intercept and slope.

I read ?model.offset and I'm still struggling to use it for my
purpose. If I understood
the concepts correctly, offset can be used to define a known
coefficient of a model,
so therefore I could create two models based on the same data like my
original one
 with an additional offset term (one model with intercept specified
and one with the
slope specified)?

Sorry for troubling you: I struggling with the data analysis of my
bachelor thesis and
just want to compare the coefficients of my linear regression to
published ones...
a method often used I guess, but still I cannot find any appropriate



> On Aug 8, 2009, Katharina May <may.katharina at googlemail.com> wrote:
> Hi there,
> I've got a question which is really trivial for sure but still I have
> to ask as I'm not
> making any progress solving it by myself (please be patient with an
> undergraduate
> student):
> I've got a linear model (lm and lmer fitted with method="ML").
> Now I want to compare the coefficients (slope, intercept, not the
> random effects)
> of both models with a given value (e.g. intercept=0.5, slope=2) to see
> if the values
> estimated with the models are significantly different from the given values.
> I heard about t.test, but I'm sorry to say that I'm not quite
> understanding what I have
> to provide as arguments.
> I would be more than happy if somebody can point out an example similar to
> the
> comparison I have to do...
> Thanks,
> Katharina
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