structure(list(study = c("4", "4", "5", "5", "6", "6", "7", "7"
), treatment = c("3", "4", "3", "4", "4", "5", "4", "5"), diff = c(NA, 
-0.35, NA, 0.55, NA, -0.3, NA, -0.3), std.err = c(NA, 0.441941738, 
NA, 0.555114559, NA, 0.274276316, NA, 0.320087245)), row.names = c(NA, 
-8L), class = "data.frame")