How many time points do I need?
This is a difficult question since it will be related to the number of variables you are using. Rules of thumb for any analysis can generally be used: the more the better! Having at least 100 time points is recommended, but adequate results have been obtained in simulation studies with only T = 60 and 5 or 10 variables (Lane et al., In Press).
Do all individuals have to have the same number of observations (T)?
No.
How many people do I need in my sample?
For regular gimme, reliable results are obtained with as few as 10 participants. Remember that in this context, power to detect effects is determined by the number of time points rather than the number of individuals. Still, having at least 10 individuals helps gimme to detect signal from noise by looking for effects that consistently occur (Gates & Molenaar, 2012).
If you wish to cluster individuals into subgroups based on similarities in their temporal patterns (i.e., uSEM pattern and weights) using S-GIMME, we recommend having at least an N of at least 25 individuals in total.
What do I do if I obtain an error? Do some initial trouble-shooting.
- Ensure that all of your individuals have the same number of variables (columns) in their data sets.
- Ensure that all variables have variability (i.e., are not constant). gimme will let you know if this is the case.
- Ensure your directories for your data are correct, and no other files are in this directory.
- Ensure that the columns are variables and the rows contain the observations across time.
- If all this is correct, please email the error you received, code used to run gimme, and the de-identified data (we promise not to use it or share it!) to: gimme@unc.edu.