diff --git a/data/Rubin1981.R b/data/Rubin1981.R
index 814a4e1596ead143aa737a59ad4a421e6a398d43..c41b46af34b13072bf4c011824ba48649fa142de 100644
--- a/data/Rubin1981.R
+++ b/data/Rubin1981.R
@@ -6,6 +6,7 @@
 #
 
 Rubin1981 <- data.frame("school"=c("A","B","C","D","E","F","G","H"),
-                         "effect"=c(28.39, 7.94, -2.75, 6.82, -0.64, 0.63, 18.01, 12.16),
-                         "stderr"=c(14.9, 10.2, 16.3, 11.0, 9.4, 11.4, 10.4, 17.6),
-                         stringsAsFactors=FALSE)
+                        "n"=as.integer(c(50, 79, 39, 91, 99, 72, 94, 35)),
+                        "effect"=c(28.39, 7.94, -2.75, 6.82, -0.64, 0.63, 18.01, 12.16),
+                        "stderr"=c(14.9, 10.2, 16.3, 11.0, 9.4, 11.4, 10.4, 17.6),
+                        stringsAsFactors=FALSE)
diff --git a/man/Rubin1981.Rd b/man/Rubin1981.Rd
index 8a79ae56aaeb54f1b6a5ad989a18cd5e0b616381..0ee7d771af29d587208a55399276f8723e02f668 100644
--- a/man/Rubin1981.Rd
+++ b/man/Rubin1981.Rd
@@ -7,6 +7,7 @@
 \format{The data frame contains the following columns:
   \tabular{lll}{
     \bold{school} \tab \code{character} \tab school identifier \cr
+    \bold{n}      \tab \code{integer}   \tab number of students \cr
     \bold{effect} \tab \code{numeric}   \tab effect estimate \cr
     \bold{stderr} \tab \code{numeric}   \tab associated standard error 
   }