diff --git a/doc/18_outliers.md b/doc/18_outliers.md
new file mode 100644
index 0000000..f557529
--- /dev/null
+++ b/doc/18_outliers.md
@@ -0,0 +1,163 @@
+## Outlier Detection
+
+This set of functions detects the presence of outliers. There are three functions for finding outliers from non-spatial data:
+
+1. Static Outliers
+1. Percentage Outliers
+1. Standard Deviation Outliers
+
+### CDB_StaticOutlier(column_value numeric, threshold numeric)
+
+#### Arguments
+
+| Name | Type | Description |
+|------|------|-------------|
+| column_value | numeric | The column of values on which to apply the threshold |
+| threshold | numeric | The static threshold which is used to indicate whether a `column_value` is an outlier or not |
+
+### Returns
+
+Returns a boolean (true/false) depending on whether a value is above or below (or equal to) the threshold
+
+| Name | Type | Description |
+|------|------|-------------|
+| outlier | boolean | classification of whether a row is an outlier or not |
+
+#### Example Usage
+
+With a table `website_visits` and a column of the number of website visits in units of 10,000 visits:
+
+```
+| id | visits_10k |
+|----|------------|
+| 1  | 1 |
+| 2  | 3 |
+| 3  | 5 |
+| 4  | 1 |
+| 5  | 32 |
+| 6  | 3 |
+| 7  | 57 |
+| 8  | 2 |
+```
+
+```sql
+SELECT
+  id,
+  CDB_StaticOutlier(visits_10k, 11.0) As outlier,
+  visits_10k
+FROM website_visits
+```
+
+```
+| id | outlier | visits_10k |
+|----|---------|------------|
+| 1  | f | 1 |
+| 2  | f | 3 |
+| 3  | f | 5 |
+| 4  | f | 1 |
+| 5  | t | 32 |
+| 6  | f | 3 |
+| 7  | t | 57 |
+| 8  | f | 2 |
+```
+
+### CDB_PercentOutlier(column_values numeric[], outlier_fraction numeric, ids int[])
+
+`CDB_PercentOutlier` calculates whether or not a value falls above a given threshold based on a percentage above the mean value of the input values.
+
+#### Arguments
+
+| Name | Type | Description |
+|------|------|-------------|
+| column_values | numeric[] | An array of the values to calculate the outlier classification on |
+| outlier_fraction | numeric | The threshold above which a column value divided by the mean of all values is considered an outlier |
+| ids | int[] | An array of the unique row ids of the input data (usually `cartodb_id`) |
+
+### Returns
+
+Returns a table of the outlier classification with the following columns
+
+| Name | Type | Description |
+|------|------|-------------|
+| is_outlier | boolean  | classification of whether a row is an outlier or not |
+| rowid | int | original row id (e.g., input `cartodb_id`) of the row which has the outlier classification |
+
+#### Example Usage
+
+This example find outliers which are more than 100% larger than the average (that is, more than 2.0 times larger).
+
+```sql
+WITH cte As (
+  SELECT
+    unnest(Array[1,2,3,4,5,6,7,8]) As id,
+    unnest(Array[1,3,5,1,32,3,57,2]) As visits_10k
+  )
+SELECT
+  (CDB_PercentOutlier(array_agg(visits_10k), 2.0, array_agg(id))).*
+FROM cte;
+```
+
+Output
+```
+| outlier | rowid |
+|---------+-------|
+| f | 1 |
+| f | 2 |
+| f | 3 |
+| f | 4 |
+| t | 5 |
+| f | 6 |
+| t | 7 |
+| f | 8 |
+```
+
+### CDB_StdDevOutlier(column_values numeric[], num_deviations numeric, ids int[], is_symmetric boolean DEFAULT true)
+
+`CDB_StdDevOutlier` calculates whether or not a value falls above or below a given threshold based on the number of standard deviations from the mean.
+
+#### Arguments
+
+| Name | Type | Description |
+|------|------|-------------|
+| column_values | numeric[] | An array of the values to calculate the outlier classification on |
+| num_deviations | numeric | The threshold in units of standard deviation |
+| ids | int[] | An array of the unique row ids of the input data (usually `cartodb_id`) |
+| is_symmetric (optional) | boolean | Consider outliers that are symmetric about the mean (default: true) |
+
+### Returns
+
+Returns a table of the outlier classification with the following columns
+
+| Name | Type | Description |
+|------|------|-------------|
+| is_outlier | boolean  | classification of whether a row is an outlier or not |
+| rowid | int | original row id (e.g., input `cartodb_id`) of the row which has the outlier classification |
+
+#### Example Usage
+
+This example find outliers which are more than 100% larger than the average (that is, more than 2.0 times larger).
+
+```sql
+WITH cte As (
+  SELECT
+    unnest(Array[1,2,3,4,5,6,7,8]) As id,
+    unnest(Array[1,3,5,1,32,3,57,2]) As visits_10k
+  )
+SELECT
+  (CDB_StdDevOutlier(array_agg(visits_10k), 2.0, array_agg(id))).*
+FROM cte;
+```
+
+Output
+```
+| outlier | rowid |
+|---------+-------|
+| f | 1 |
+| f | 2 |
+| f | 3 |
+| f | 4 |
+| f | 5 |
+| f | 6 |
+| t | 7 |
+| f | 8 |
+```
diff --git a/src/pg/sql/18_outliers.sql b/src/pg/sql/18_outliers.sql
new file mode 100644
index 0000000..5b23c77
--- /dev/null
+++ b/src/pg/sql/18_outliers.sql
@@ -0,0 +1,75 @@
+
+-- Find outliers using a static threshold
+--
+CREATE OR REPLACE FUNCTION CDB_StaticOutlier(column_value numeric, threshold numeric)
+RETURNS boolean
+AS $$
+BEGIN
+
+  RETURN column_value > threshold;
+
+END;
+$$ LANGUAGE plpgsql;
+
+-- Find outliers by a percentage above the threshold
+-- TODO: add symmetric option? `is_symmetric boolean DEFAULT false`
+
+CREATE OR REPLACE FUNCTION CDB_PercentOutlier(column_values numeric[], outlier_fraction numeric, ids int[])
+RETURNS TABLE(is_outlier boolean, rowid int)
+AS $$
+DECLARE
+  avg_val numeric;
+  out_vals boolean[];
+BEGIN
+
+  SELECT avg(i) INTO avg_val
+    FROM unnest(column_values) As x(i);
+
+  IF avg_val = 0 THEN
+    RAISE EXCEPTION 'Mean value is zero. Try another outlier method.';
+  END IF;
+
+  SELECT array_agg(
+           outlier_fraction < i / avg_val) INTO out_vals
+    FROM unnest(column_values) As x(i);
+
+  RETURN QUERY
+  SELECT unnest(out_vals) As is_outlier,
+         unnest(ids) As rowid;
+
+END;
+$$ LANGUAGE plpgsql;
+
+-- Find outliers above a given number of standard deviations from the mean
+
+CREATE OR REPLACE FUNCTION CDB_StdDevOutlier(column_values numeric[], num_deviations numeric, ids int[], is_symmetric boolean DEFAULT true)
+RETURNS TABLE(is_outlier boolean, rowid int)
+AS $$
+DECLARE
+  stddev_val numeric;
+  avg_val numeric;
+  out_vals boolean[];
+BEGIN
+
+  SELECT stddev(i), avg(i) INTO stddev_val, avg_val
+    FROM unnest(column_values) As x(i);
+
+  IF stddev_val = 0 THEN
+    RAISE EXCEPTION 'Standard deviation of input data is zero';
+  END IF;
+
+  IF is_symmetric THEN
+    SELECT array_agg(
+             abs(i - avg_val) / stddev_val > num_deviations) INTO out_vals
+      FROM unnest(column_values) As x(i);
+  ELSE
+    SELECT array_agg(
+             (i - avg_val) / stddev_val > num_deviations) INTO out_vals
+      FROM unnest(column_values) As x(i);
+  END IF;
+
+  RETURN QUERY
+  SELECT unnest(out_vals) As is_outlier,
+         unnest(ids) As rowid;
+END;
+$$ LANGUAGE plpgsql;
diff --git a/src/pg/test/expected/18_outliers_test.out b/src/pg/test/expected/18_outliers_test.out
new file mode 100644
index 0000000..0798e0c
--- /dev/null
+++ b/src/pg/test/expected/18_outliers_test.out
@@ -0,0 +1,23 @@
+SET client_min_messages TO WARNING;
+\set ECHO none
+is_outlier|rowid
+t|11
+t|16
+t|17
+(3 rows)
+is_outlier|rowid
+t|16
+t|17
+(2 rows)
+ERROR:  Standard deviation of input data is zero
+is_outlier|rowid
+t|8
+t|11
+t|16
+(3 rows)
+is_outlier|rowid
+t|8
+t|9
+t|11
+t|16
+(4 rows)
diff --git a/src/pg/test/sql/18_outliers_test.sql b/src/pg/test/sql/18_outliers_test.sql
new file mode 100644
index 0000000..9a6b87d
--- /dev/null
+++ b/src/pg/test/sql/18_outliers_test.sql
@@ -0,0 +1,85 @@
+SET client_min_messages TO WARNING;
+\set ECHO none
+\pset format unaligned
+
+--
+-- postgres=# select round(avg(i), 3) as avg,
+--                   round(stddev(i), 3) as stddev,
+--                   round(avg(i) + stddev(i), 3) as one_stddev,
+--                   round(avg(i) + 2 * stddev(i), 3) As two_stddev
+--            from unnest(ARRAY[1,3,2,3,5,1,2,32,12,3,57,2,1,4,2,100]) As x(i);
+--   avg   | stddev | one_stddev | two_stddev
+-- --------+--------+------------+------------
+--  14.375 | 27.322 |     41.697 |     69.020
+
+
+-- With an threshold of 1.0 standard deviation, ids 11, 16, and 17 are outliers
+WITH a AS (
+    SELECT
+      ARRAY[1,3,2,3,5,1,2,32,12, 3,57, 2, 1, 4, 2,100,-100]::numeric[] As vals, ARRAY[1,2,3,4,5,6,7, 8, 9,10,11,12,13,14,15, 16,  17]::int[] As ids
+), b As (
+  SELECT
+    (cdb_crankshaft.cdb_StdDevOutlier(vals, 1.0, ids)).*
+  FROM a
+  ORDER BY ids)
+SELECT *
+FROM b
+WHERE is_outlier IS TRUE;
+
+-- With a threshold of 2.0 standard deviations, id 16 is the only outlier
+WITH a AS (
+    SELECT
+      ARRAY[1,3,2,3,5,1,2,32,12, 3,57, 2, 1, 4, 2,100,-100]::numeric[] As vals,
+      ARRAY[1,2,3,4,5,6,7, 8, 9,10,11,12,13,14,15, 16,  17]::int[] As ids
+), b As (
+  SELECT
+    (cdb_crankshaft.CDB_StdDevOutlier(vals, 2.0, ids)).*
+  FROM a
+  ORDER BY ids)
+SELECT *
+FROM b
+WHERE is_outlier IS TRUE;
+
+-- With a Stddev of zero, should throw back error
+-- With a threshold of 2.0 standard deviations, id 16 is the only outlier
+WITH a AS (
+    SELECT
+      ARRAY[5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5]::numeric[] As vals,
+      ARRAY[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16]::int[] As ids
+), b As (
+  SELECT
+    (cdb_crankshaft.CDB_StdDevOutlier(vals, 1.0, ids)).*
+  FROM a
+  ORDER BY ids)
+SELECT *
+FROM b
+WHERE is_outlier IS TRUE;
+
+-- With a ratio threshold of 2.0 threshold (100% above or below the mean)
+--  which is greater than ~21, which are values
+WITH a AS (
+    SELECT
+      ARRAY[1,3,2,3,5,1,2,32,12, 3,57, 2, 1, 4, 2,100,-100]::numeric[] As vals,
+      ARRAY[1,2,3,4,5,6,7, 8, 9,10,11,12,13,14,15, 16,  17]::int[] As ids
+), b As (
+  SELECT
+    (cdb_crankshaft.CDB_PercentOutlier(vals, 2.0, ids)).*
+  FROM a
+  ORDER BY ids)
+SELECT *
+  FROM b
+ WHERE is_outlier IS TRUE;
+
+-- With a static threshold of 11, what are the outliers
+WITH a AS (
+     SELECT
+       ARRAY[1,3,2,3,5,1,2,32,12, 3,57, 2, 1, 4, 2,100,-100]::numeric[] As vals,
+       ARRAY[1,2,3,4,5,6,7, 8, 9,10,11,12,13,14,15, 16,  17]::int[] As ids
+ ), b As (
+   SELECT unnest(vals) As v, unnest(ids) as i
+     FROM a
+ )
+SELECT cdb_crankshaft.CDB_StaticOutlier(v, 11.0) As is_outlier, i As rowid
+  FROM b
+WHERE cdb_crankshaft.CDB_StaticOutlier(v, 11.0) is True
+ORDER BY i;