study	treatment	diff	std.err
4    	C        	NA      NA
4    	D        	-0.35	0.441941738
5    	C        	NA      NA
5    	D        	0.55	0.555114559
6    	D        	NA      NA
6    	E        	-0.3    0.274276316
7    	D        	NA      NA
7    	E        	-0.3	0.320087245
