diff --git a/R/splines.R b/R/splines.R
index 7e12e9c..dc18149 100644
--- a/R/splines.R
+++ b/R/splines.R
@@ -1,6 +1,6 @@
 pgbeta <- function(x, mu = .5, sig = 1, nonc = 0) {
-    a <- mu * sig * 2
-    b <- (1 - mu) * sig * 2
+    a <- (1 - mu) * sig * 2
+    b <- mu * sig * 2
     c <- abs(nonc)
     seq_beta <- pbeta(x, a, b, c)
     if (nonc < 0) seq_beta <- rev(1 - seq_beta)