[R] Heteroscedastic data due to responses at one factor level being too low to measure and assumed to be 0?
Dr. Leigh S. Sutherland
l.sutherland at tecnico.ulisboa.pt
Tue Mar 1 16:01:05 CET 2016
I have a 3-factor experimental design.
The response is the load to break an adhesive joint.
I have a question about Heteroscedastic data ('non-uniform variability',
Google told me that's what it's called - I'm not a statistician, just an
- At one level of a factor the response values are so low to make them
un-testable and they have to be assumed to be 0
- However this gives no variability at that level since all responses
are 0, (although in reality they may well have similar variability as at
- This gives heteroscedastic data across the levels of the factor
- What implications does this have for stats tests that are sensitive to
- If I need to do anything, what can I do? can I 'superimpose' the same
variability on level 1 results to give artificial variable values 'around'
0kg? (this would not at all invalidate the data's validity)
Centre for Marine Technology and Ocean Engineering (CENTEC)
Instituto Superior Técnico
Av. Rovisco Pais
Tel: +351 218 417 947
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