Dear R gurus, I am using the "lsmeans" function to extract predicted marginal means from a Poisson family mixed model with a log link function. When I ask for the "lsmeans" on the scale of the linear predictor, the standard errors and confidence limits are symmetrical about the mean. However, I would like to plot the responses on the original scale, so that I can depict "number of eggs" rather than "ln(number of eggs)". The function "lsmeans" offers this reverse transformation via the argument "type='response'". However, I don't understand why there is only one standard error after the response. When I manually exponentiate the predicted means and CI's from the scale of the linear predictor to the scale of the original response variable, my calculations match perfectly. However, when I exponentiate the "mean + se" and "mean - se" for plotting on the original scale, I get asymmetric bars. So in lsmeans, what does the "SE" mean when using "type="response""? Shouldn't there be separate + and - SE values? The SE value seems to be very close to (upperCI-lowerCI)/4, but not exactly. Should I plot mean +/- SE using "type="response"" for symmetric error bars, or use my manually exponentiated mean +/-SE? Thanks for your help! Evan
LSmean: transformed error bars
1 message · Evan Palmer-Young