diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5c007c4a..f6cca4c8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
     - `fit_curve`
     - `predict_curve`
 - `run_udf`: Exception `InvalidRuntime` added
+- A new category "math > statistics" has been added [#277](https://github.com/Open-EO/openeo-processes/issues/277)
 
 ### Changed
 
@@ -25,6 +26,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - `aggregate_temporal_period`: Clarified which dimension labels are present in the returned data cube. [#274](https://github.com/Open-EO/openeo-processes/issues/274)
 - `ard_surface_reflectance`: has been categorized as "optical" instead of "sar".
+- `quantiles`: Clarified behavior. [#278](https://github.com/Open-EO/openeo-processes/issues/278)
 
 ## [1.1.0] - 2021-06-29
 
diff --git a/count.json b/count.json
index ed1044bd..c2de1451 100644
--- a/count.json
+++ b/count.json
@@ -4,6 +4,7 @@
     "description": "Gives the number of elements in an array that matches the specified condition.\n\n**Remarks:**\n\n* Counts the number of valid elements by default (`condition` is set to `null`). A valid element is every element for which ``is_valid()`` returns `true`.\n* To count all elements in a list set the `condition` parameter to boolean `true`.",
     "categories": [
         "arrays",
+        "math > statistics",
         "reducer"
     ],
     "parameters": [
diff --git a/extrema.json b/extrema.json
index e2503f04..6f6075de 100644
--- a/extrema.json
+++ b/extrema.json
@@ -3,7 +3,7 @@
     "summary": "Minimum and maximum values",
     "description": "Two element array containing the minimum and the maximum values of `data`.\n\nThis process is basically an alias for calling both ``min()`` and ``max()``, but may be implemented more performant by back-ends as it only needs to iterate over the data once instead of twice.",
     "categories": [
-        "math"
+        "math > statistics"
     ],
     "parameters": [
         {
diff --git a/max.json b/max.json
index 5a5b7f71..d8903df0 100644
--- a/max.json
+++ b/max.json
@@ -4,6 +4,7 @@
     "description": "Computes the largest value of an array of numbers, which is equal to the first element of a sorted (i.e., ordered) version of the array.\n\nAn array without non-`null` elements resolves always with `null`.",
     "categories": [
         "math",
+        "math > statistics",
         "reducer"
     ],
     "parameters": [
diff --git a/mean.json b/mean.json
index 31a5ea42..cb45faa4 100644
--- a/mean.json
+++ b/mean.json
@@ -3,7 +3,7 @@
     "summary": "Arithmetic mean (average)",
     "description": "The arithmetic mean of an array of numbers is the quantity commonly called the average. It is defined as the sum of all elements divided by the number of elements.\n\nAn array without non-`null` elements resolves always with `null`.",
     "categories": [
-        "math",
+        "math > statistics",
         "reducer"
     ],
     "parameters": [
diff --git a/median.json b/median.json
index 3bc87d5a..e54deb84 100644
--- a/median.json
+++ b/median.json
@@ -3,7 +3,7 @@
     "summary": "Statistical median",
     "description": "The statistical median of an array of numbers is the value separating the higher half from the lower half of the data.\n\nAn array without non-`null` elements resolves always with `null`.\n\n**Remarks:**\n\n* For symmetric arrays, the result is equal to the ``mean()``.\n* The median can also be calculated by computing the ``quantiles()`` with a probability of *0.5*.",
     "categories": [
-        "math",
+        "math > statistics",
         "reducer"
     ],
     "parameters": [
diff --git a/min.json b/min.json
index ce161c95..26c60882 100644
--- a/min.json
+++ b/min.json
@@ -4,6 +4,7 @@
     "description": "Computes the smallest value of an array of numbers, which is equal to the last element of a sorted (i.e., ordered) version of the array.\n\nAn array without non-`null` elements resolves always with `null`.",
     "categories": [
         "math",
+        "math > statistics",
         "reducer"
     ],
     "parameters": [
diff --git a/quantiles.json b/quantiles.json
index 35079b86..bc4153fb 100644
--- a/quantiles.json
+++ b/quantiles.json
@@ -1,9 +1,9 @@
 {
     "id": "quantiles",
     "summary": "Quantiles",
-    "description": "Calculates quantiles, which are cut points dividing the range of a probability distribution into either\n\n* intervals corresponding to the given `probabilities` or\n* (nearly) equal-sized intervals (q-quantiles based on the parameter `q`).\n\nEither the parameter `probabilities` or `q` must be specified, otherwise the `QuantilesParameterMissing` exception is thrown. If both parameters are set the `QuantilesParameterConflict` exception is thrown.",
+    "description": "Calculates quantiles, which are cut points dividing the range of a probability distribution into either\n\n* intervals corresponding to the given `probabilities` or\n* equal-sized intervals (q-quantiles based on the parameter `q`).\n\nEither the parameter `probabilities` or `q` must be specified, otherwise the `QuantilesParameterMissing` exception is thrown. If both parameters are set the `QuantilesParameterConflict` exception is thrown.",
     "categories": [
-        "math"
+        "math > statistics"
     ],
     "parameters": [
         {
@@ -21,7 +21,7 @@
         },
         {
             "name": "probabilities",
-            "description": "A list of probabilities to calculate quantiles for. The probabilities must be between 0 and 1.",
+            "description": "A list of probabilities to calculate quantiles for. The probabilities must be between 0 and 1 (inclusive).",
             "schema": {
                 "type": "array",
                 "items": {
@@ -34,7 +34,7 @@
         },
         {
             "name": "q",
-            "description": "Intervals to calculate quantiles for. Calculates q-quantiles with (nearly) equal-sized intervals.",
+            "description": "Number of intervals to calculate quantiles for. Calculates q-quantiles with equal-sized intervals.",
             "schema": {
                 "type": "integer",
                 "minimum": 2
diff --git a/sd.json b/sd.json
index 89be4f70..156e4b38 100644
--- a/sd.json
+++ b/sd.json
@@ -3,7 +3,7 @@
     "summary": "Standard deviation",
     "description": "Computes the sample standard deviation, which quantifies the amount of variation of an array of numbers. It is defined to be the square root of the corresponding variance (see ``variance()``).\n\nA low standard deviation indicates that the values tend to be close to the expected value, while a high standard deviation indicates that the values are spread out over a wider range.\n\nAn array without non-`null` elements resolves always with `null`.",
     "categories": [
-        "math",
+        "math > statistics",
         "reducer"
     ],
     "parameters": [
diff --git a/variance.json b/variance.json
index 8d9acbeb..78f76feb 100644
--- a/variance.json
+++ b/variance.json
@@ -3,7 +3,7 @@
     "summary": "Variance",
     "description": "Computes the sample variance of an array of numbers by calculating the square of the standard deviation (see ``sd()``). It is defined to be the expectation of the squared deviation of a random variable from its expected value. Basically, it measures how far the numbers in the array are spread out from their average value.\n\nAn array without non-`null` elements resolves always with `null`.",
     "categories": [
-        "math",
+        "math > statistics",
         "reducer"
     ],
     "parameters": [