diff --git a/README.md b/README.md
index 217bc55..2610ea2 100644
--- a/README.md
+++ b/README.md
@@ -77,9 +77,8 @@ Behaviour on error can be toggled by the `EXIT_ON_ERROR` variable. This library
 
 ## To do list
 
-- [ ] Rename functions to something more self-explanatory, e.g,. sample_sample_sample_unit_normal.
 - [ ] Have some more complicated & realistic example
-- [ ] Add summarization functions, like mean, std, 90% ci (or all c.i.?)
+- [ ] Add summarization functions: 90% ci (or all c.i.?) 
 - [ ] Publish online
 - [ ] Support all distribution functions in <https://www.squiggle-language.com/docs/Api/Dist>
 - [ ] Support all distribution functions in <https://www.squiggle-language.com/docs/Api/Dist>, and do so efficiently
@@ -105,3 +104,5 @@ Behaviour on error can be toggled by the `EXIT_ON_ERROR` variable. This library
   - [x] Explain nested functions
   - [x] Explain exit on error
   - [x] Explain individual examples
+- [x] Rename functions to something more self-explanatory, e.g,. `sample_unit_normal`.
+- [x] Add summarization functions: mean, std
diff --git a/squiggle.c b/squiggle.c
index 377341f..11b66f8 100644
--- a/squiggle.c
+++ b/squiggle.c
@@ -76,11 +76,11 @@ float sample_to(float low, float high, uint32_t* seed)
 // Array helpers
 float array_sum(float* array, int length)
 {
-    float output = 0.0;
+    float sum = 0.0;
     for (int i = 0; i < length; i++) {
-        output += array[i];
+        sum += array[i];
     }
-    return output;
+    return sum;
 }
 
 void array_cumsum(float* array_to_sum, float* array_cumsummed, int length)
@@ -91,6 +91,21 @@ void array_cumsum(float* array_to_sum, float* array_cumsummed, int length)
     }
 }
 
+float array_mean(float* array, int length){
+	float sum = array_sum(array, length);
+	return sum / length;
+}
+
+float array_std(float* array, int length){
+		float mean = array_mean(array, length);
+    float std = 0.0;
+    for (int i = 0; i < length; i++) {
+        std += pow(array[i] - mean, 2.0);
+    }
+		std=sqrt(std/length);
+    return std;
+}
+
 // Mixture function
 float sample_mixture(float (*samplers[])(uint32_t*), float* weights, int n_dists, uint32_t* seed)
 {
diff --git a/squiggle.h b/squiggle.h
index 21c6231..84d95eb 100644
--- a/squiggle.h
+++ b/squiggle.h
@@ -20,6 +20,8 @@ float sample_to(float low, float high, uint32_t* seed);
 // Array helpers
 float array_sum(float* array, int length);
 void array_cumsum(float* array_to_sum, float* array_cumsummed, int length);
+float array_mean(float* array, int length);
+float array_std(float* array, int length);
 
 // Mixture function
 float sample_mixture(float (*samplers[])(uint32_t*), float* weights, int n_dists, uint32_t* seed);