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diff --git a/src/main/java/org/apache/commons/math3/stat/descriptive/UnivariateStatistic.java b/src/main/java/org/apache/commons/math3/stat/descriptive/UnivariateStatistic.java
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+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.commons.math3.stat.descriptive;
+
+import org.apache.commons.math3.exception.MathIllegalArgumentException;
+import org.apache.commons.math3.util.MathArrays;
+
+
+/**
+ * Base interface implemented by all statistics.
+ *
+ */
+public interface UnivariateStatistic extends MathArrays.Function {
+    /**
+     * Returns the result of evaluating the statistic over the input array.
+     *
+     * @param values input array
+     * @return the value of the statistic applied to the input array
+     * @throws MathIllegalArgumentException  if values is null
+     */
+    double evaluate(double[] values) throws MathIllegalArgumentException;
+
+    /**
+     * Returns the result of evaluating the statistic over the specified entries
+     * in the input array.
+     *
+     * @param values the input array
+     * @param begin the index of the first element to include
+     * @param length the number of elements to include
+     * @return the value of the statistic applied to the included array entries
+     * @throws MathIllegalArgumentException if values is null or the indices are invalid
+     */
+    double evaluate(double[] values, int begin, int length) throws MathIllegalArgumentException;
+
+    /**
+     * Returns a copy of the statistic with the same internal state.
+     *
+     * @return a copy of the statistic
+     */
+    UnivariateStatistic copy();
+}