diff --git a/src/histogram.hpp b/src/histogram.hpp
new file mode 100644
index 0000000000000000000000000000000000000000..8dfce4b513d463deb17e901d1543a360efe5cc61
--- /dev/null
+++ b/src/histogram.hpp
@@ -0,0 +1,8 @@
+#ifndef PROGAUT_UEBUNG6_HISTOGRAM_HPP
+#define PROGAUT_UEBUNG6_HISTOGRAM_HPP
+
+#include <vector>
+
+int getMostFrequentValue(const std::vector<int>& data);
+
+#endif  // PROGAUT_UEBUNG6_HISTOGRAM_HPP
diff --git a/src/outliers.hpp b/src/outliers.hpp
new file mode 100644
index 0000000000000000000000000000000000000000..604ea0131ed225ab1a4830ed4021e11233e0c56e
--- /dev/null
+++ b/src/outliers.hpp
@@ -0,0 +1,12 @@
+#ifndef PROGAUT_UEBUNG6_OUTLIERS_HPP
+#define PROGAUT_UEBUNG6_OUTLIERS_HPP
+
+#include <vector>
+#include <cstddef>
+#include <cmath>
+
+double findNMin(const std::vector<double>& data, size_t n);
+double findNMax(const std::vector<double>& data, size_t n);
+std::vector<double> removeOutliers(std::vector<double> data, size_t n);
+
+#endif  // PROGAUT_UEBUNG6_OUTLIERS_HPP
diff --git a/src/statistics.hpp b/src/statistics.hpp
new file mode 100644
index 0000000000000000000000000000000000000000..73bc18219b41bde16f31cd192573ddc500167ccf
--- /dev/null
+++ b/src/statistics.hpp
@@ -0,0 +1,8 @@
+#ifndef PROGAUT_UEBUNG6_STATISTICS_HPP
+#define PROGAUT_UEBUNG6_STATISTICS_HPP
+
+#include <vector>
+#include <cstddef>
+size_t countValuesNearMean(const std::vector<double>& data);
+
+#endif  // PROGAUT_UEBUNG6_STATISTICS_HPP