Sorry, I did not see your last line. Yes, create a single variable that is categorical. Again, here is the continuation of my example: . regress y i.ord_treat [pw= cem_weights] . margins ord_treat, pwcompare(effects) mcompare(bonferroni) So here I have run a regression in which the outcome Y is continuous, and treatment is a categorical variable called “ord_treat” I then run margins to get all pairwise comparisons with Bonferroni adjustment for multiple tests Ariel *From:* cem-bounces(a)lists.gking.harvard.edu [mailto: cem-bounces(a)lists.gking.harvard.edu] *On Behalf Of *Erik Cleven *Sent:* Wednesday, November 11, 2015 4:21 PM *Cc:* cem(a)lists.gking.harvard.edu *Subject:* Re: [cem] cem error message Thanks, Ariel! Because of the error message cem does not calculate cem_weights. I am therefore not able to run a regression model after cem preprocessing the data. I assume that when you have more than two treatments is it correct to use one treatment variable that is coded as a categorical variable, right? Erik On Wed, Nov 11, 2015 at 4:06 PM, Ariel Linden &lt;ariel.linden(a)gmail.com&gt; wrote: You can certainly specify more than 2 treatments. The error you’re getting is because –imbalance- is set up to compare between only two treatment groups. As for the k2k error, I don’t get that error. However, I do find that k2k does not produce 1:1 matches when there are more than two treatments. *From:* cem-bounces(a)lists.gking.harvard.edu [mailto: cem-bounces(a)lists.gking.harvard.edu] *On Behalf Of *Erik Cleven *Sent:* Wednesday, November 11, 2015 3:59 PM *To:* cem(a)lists.gking.harvard.edu *Subject:* [cem] cem error message I am attempting to run cem with an ordinal treatment variable that has four values. I get the following error message: imbalance(): 3258 <tmp>[1,1] found where void required <istmt>: - function returned error r(3258); A previous reply to someone who also got this error message said to update cem because there was a bug with the imb function. I updated and now recieve this message: NOTE: Treatment has must have only 2 levels to compute distance and weights. In addition, k2k cannot be used. Does this mean cem cannot be used with more than 2 treatments? Actually I have a continuous treatment but I recoded it to a variable with four levels. Thanks! Erik -- Erik Cleven, PhD Assistant Professor Department of Politics Saint Anselm College 100 Saint Anselm Drive Manchester, NH 03102-1310 E-mail: ecleven(a)anselm.edu Office Phone: (603) 222-4119 Cell phone: (603) 867-8732 - -- cem Mailing List, served by HUIT Send messages: cem(a)lists.gking.harvard.edu [un]subscribe Options: http://lists.gking.harvard.edu/?info=cem More information on cem: http://gking.harvard.edu/cem Cem mailing list Cem(a)lists.gking.harvard.edu To unsubscribe from this list or get other information: https://lists.gking.harvard.edu/mailman/listinfo/cem -- Erik Cleven, PhD Assistant Professor Department of Politics Saint Anselm College 100 Saint Anselm Drive Manchester, NH 03102-1310 E-mail: ecleven(a)anselm.edu Office Phone: (603) 222-4119 Cell phone: (603) 867-8732