diff --git a/src/main/java/blog/common/Util.java b/src/main/java/blog/common/Util.java
index e12fc14f..61b1aa6c 100644
--- a/src/main/java/blog/common/Util.java
+++ b/src/main/java/blog/common/Util.java
@@ -1088,7 +1088,7 @@ public static boolean closeToZero(double number) {
      * note a single precision can represent up to 1E-38
      * double precision 1E-308
      */
-    final double APPROXIMATE_ZERO = 1e-20;
+    final double APPROXIMATE_ZERO = 1e-12;
     return (number < APPROXIMATE_ZERO) && (number > -1 * APPROXIMATE_ZERO);
   }
 
diff --git a/src/main/java/blog/distrib/InverseWishart.java b/src/main/java/blog/distrib/InverseWishart.java
index ba2e2040..8f6ddc11 100644
--- a/src/main/java/blog/distrib/InverseWishart.java
+++ b/src/main/java/blog/distrib/InverseWishart.java
@@ -174,6 +174,7 @@ public double getLogProb(MatrixLib x) {
     }
     throw new IllegalArgumentException(
         "The matrix given should be a symmetric one. But it isn't.");
+
   }
 
   /*
diff --git a/src/main/java/blog/distrib/NoisyOr.java b/src/main/java/blog/distrib/NoisyOr.java
new file mode 100644
index 00000000..90f4dea1
--- /dev/null
+++ b/src/main/java/blog/distrib/NoisyOr.java
@@ -0,0 +1,95 @@
+/**
+ * 
+ */
+package blog.distrib;
+
+import blog.common.Util;
+import blog.common.numerical.MatrixLib;
+
+/**
+ * @author BEN
+ * @since Dec 6, 2014
+ * 
+ */
+public class NoisyOr implements CondProbDistrib {
+
+  @Override
+  public void setParams(Object[] params) {
+    if (params.length != 2) {
+      throw new IllegalArgumentException("expected two parameters");
+    }
+    setParams((MatrixLib) params[0], (MatrixLib) params[1]);
+  }
+
+  public void setParams(MatrixLib b, MatrixLib p) {
+    if (b != null) {
+      this.b = b;
+      this.hasb = true;
+    }
+    if (p != null) {
+      this.p = p;
+      this.hasp = true;
+    }
+    if (this.hasb && this.hasp) {
+      initializeConstants();
+    }
+  }
+
+  private void initializeConstants() {
+    this.prob = 1.0 - this.b.transpose().timesMat(this.p).det();
+  }
+
+  private void checkHasParams() {
+    if (!this.hasp && !this.hasb) {
+      throw new IllegalArgumentException("parameter p not provided");
+    }
+  }
+
+  @Override
+  public double getProb(Object value) {
+    return getProb(((Boolean) value).booleanValue());
+  }
+
+  public double getProb(boolean value) {
+    checkHasParams();
+    if (value) {
+      return this.prob;
+    }
+    return 1 - this.prob;
+  }
+
+  @Override
+  public double getLogProb(Object value) {
+    return getLogProb(((Boolean) value).booleanValue());
+  }
+
+  public double getLogProb(boolean value) {
+    checkHasParams();
+    if (value) {
+      return Math.log(this.prob);
+    }
+    return Math.log(1.0 - this.prob);
+  }
+
+  @Override
+  public Object sampleVal() {
+    checkHasParams();
+    if (Util.random() < this.prob) {
+      return true;
+    }
+    return false;
+  }
+
+  @Override
+  public Object[] getFiniteSupport() {
+    return finiteSupport;
+  }
+
+  private MatrixLib b;
+  private MatrixLib p;
+  private double prob;
+  private boolean hasb;
+  private boolean hasp;
+  private static final Object[] finiteSupport = { true, false };
+
+}