[R-sig-ME] Random slope with cross-level interaction

[Yashree Mehta]

Hi Salahadin,

Thanks for your reply. It is very helpful.

Then, is there a way I can extract the coefficient estimate of the fixed
effect of fertilizer as well as that of wheatlanduse as a main effect?

Regards,
Yashree

On Sun, Jul 19, 2020 at 6:59 PM Yashree Mehta <yashree19 using gmail.com> wrote:

> Hi Salahadin,
>
> Thanks for your reply. It is very helpful.
>
> Then, is there a way I can extract the coefficient estimate of the fixed
> effect of fertilizer as well as that of wheatlanduse as a main effect?
>
> Regards,
> Yashree
>
> On Sun, Jul 19, 2020 at 5:46 PM Salahadin Lotfi <salahadin.lotfi using gmail.com>
> wrote:
>
>> Hi Yashree,
>> The interpretation of the interaction term do change whether you include
>> the main effect of not.
>> Usually having only the interaction term in the model requires a specific
>> hypothesis. Thus, the lower level terms (i.e., the main effects) are almost
>> always included.
>> The lmer function automatically includes the lower level terms even if
>> you just include an interaction term.
>> For example, if you setup your model as follow, the main effects of
>> fertilizer and wheatlanduse will be still taken into account.
>> Production = seed + fertilizer : wheatlanduse + (1 + fertilizer |
>> Household)
>>
>> Thanks,
>> Sala
>>
>> *************
>> Salahadin (Sala) Lotfi
>>
>> PhD Candidate of Cognitive Psychology & Neuroscience
>>
>> University of Wisconsin-Milwaukee
>>
>> Anxiety Disorders Laboratory
>>
>> President, Association of Clinical and Cognitive Neuroscience, UWM
>>
>> On Sun, Jul 19, 2020 at 5:02 AM Yashree Mehta <yashree19 using gmail.com>
>> wrote:
>>
>>> Hi,
>>>
>>> I have the following model:
>>>
>>> Production = seed + fertilizer + fertilizer : wheatlanduse + (1 +
>>> fertilizer | Household)
>>>
>>> As the formula indicates, the household level is specified as the random
>>> intercept. Fertilizer is specified as random slope , and has also been
>>> specified as a fixed effect.
>>>
>>> I am interested in cross-level interaction between fertilizer and the
>>> wheatlanduse variable. So, I have inserted "fertilizer : wheatlanduse".
>>>
>>> My question is: Do I have to include "wheatlanduse" as a main effect in
>>> the
>>> formula as well? Or is it acceptable to only have it as a part of the
>>> interaction term?
>>>
>>> Thank you,
>>>
>>> Regards,
>>> Yashree
>>>
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>>>
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>>

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