diff --git a/Sprint-1/fix/median.js b/Sprint-1/fix/median.js
index 5c5b796e1..7928ccc95 100644
--- a/Sprint-1/fix/median.js
+++ b/Sprint-1/fix/median.js
@@ -6,8 +6,30 @@
 // or contains values that aren't numbers (the function is expected to throw - see the tests).
 
 function calculateMedian(list) {
-  const middleIndex = Math.floor(list.length / 2);
-  const median = list.splice(middleIndex, 1)[0];
+  if (!Array.isArray(list)) {
+    throw new Error("calculateMedian requires an array of numbers");
+  }
+  if (list.length === 0) {
+    throw new Error("calculateMedian requires a non-empty array");
+  }
+
+  if (
+    !list.every(
+      (currentValue) =>
+        typeof currentValue === "number" && !Number.isNaN(currentValue)
+    )
+  ) {
+    throw new Error("calculateMedian requires an array of numbers");
+  }
+
+  const sortedList = list.toSorted((a, b) => a - b);
+  const middleIndex = Math.floor(sortedList.length / 2);
+  let median;
+  if (sortedList.length % 2 === 0) {
+    median = (sortedList[middleIndex - 1] + sortedList[middleIndex]) / 2;
+  } else {
+    median = sortedList[middleIndex];
+  }
   return median;
 }
 
diff --git a/Sprint-1/implement/dedupe.js b/Sprint-1/implement/dedupe.js
index 781e8718a..5631aceef 100644
--- a/Sprint-1/implement/dedupe.js
+++ b/Sprint-1/implement/dedupe.js
@@ -1 +1,12 @@
-function dedupe() {}
+function dedupe(elements) {
+  const dedupedArray = [];
+
+  for (value of elements) {
+    if (!dedupedArray.includes(value)) {
+      dedupedArray.push(value);
+    }
+  }
+  return dedupedArray;
+}
+
+module.exports = dedupe;
diff --git a/Sprint-1/implement/dedupe.test.js b/Sprint-1/implement/dedupe.test.js
index d7c8e3d8e..dec42086e 100644
--- a/Sprint-1/implement/dedupe.test.js
+++ b/Sprint-1/implement/dedupe.test.js
@@ -13,16 +13,20 @@ E.g. dedupe([1, 2, 1]) returns [1, 2]
 
 // Acceptance Criteria:
 
-// Given an empty array
-// When passed to the dedupe function
-// Then it should return an empty array
-test.todo("given an empty array, it returns an empty array");
+test("given an empty array, it returns an empty array", () => {
+  expect(dedupe([])).toEqual([]);
+});
 
-// Given an array with no duplicates
-// When passed to the dedupe function
-// Then it should return a copy of the original array
+test("given an array with no duplicates, should return a copy of the same array", () => {
+  expect(dedupe([1, 5, 9, 23])).toEqual([1, 5, 9, 23]);
+});
 
-// Given an array of strings or numbers
-// When passed to the dedupe function
-// Then it should return a new array with duplicates removed while preserving the 
-// first occurrence of each element from the original array.
+test("given an array with strings or numbers, should return an array with duplicates removed and first occurrence preserved", () => {
+  expect(dedupe([1, 6, 1, "a", 5, 6, "a", "b", "b"])).toEqual([
+    1,
+    6,
+    "a",
+    5,
+    "b",
+  ]);
+});
diff --git a/Sprint-1/implement/describe-median.js b/Sprint-1/implement/describe-median.js
index 3381cfc0a..551c245f1 100644
--- a/Sprint-1/implement/describe-median.js
+++ b/Sprint-1/implement/describe-median.js
@@ -20,6 +20,18 @@ function calculateMedian(list) {
 }
 
 // Implement this function. See describe-median.test.js for the acceptance criteria.
-function describeMedian(list) {}
+function describeMedian(list) {
+  try {
+    return "The median is " + calculateMedian(list);
+  } catch {
+    if (list.length === 0) {
+      return "Could not calculate a median: calculateMedian requires a non-empty array";
+    }
+
+    if (!Array.isArray(list)) {
+      return "Could not calculate a median: calculateMedian requires an array of numbers";
+    }
+  }
+}
 
 module.exports = describeMedian;
diff --git a/Sprint-1/implement/describe-median.test.js b/Sprint-1/implement/describe-median.test.js
index e7d18a264..e12a9cf7c 100644
--- a/Sprint-1/implement/describe-median.test.js
+++ b/Sprint-1/implement/describe-median.test.js
@@ -17,16 +17,18 @@ const describeMedian = require("./describe-median.js");
 
 // Acceptance criteria:
 
-// Given an array of numbers
-// When passed to describeMedian
-// Then it should return "The median is " followed by the median
-// Delete this test.todo and replace it with a test.
-test.todo('given [1, 2, 3], returns "The median is 2"');
-
-// Given an empty array
-// When passed to describeMedian
-// Then it should return "Could not calculate a median: calculateMedian requires a non-empty array"
-
-// Given something that isn't an array of numbers, e.g. "banana"
-// When passed to describeMedian
-// Then it should return "Could not calculate a median: calculateMedian requires an array of numbers"
+test('given [1, 2, 3], returns "The median is 2"', () => {
+  expect(describeMedian([1, 2, 3])).toEqual("The median is 2");
+});
+
+test('given empty array, returns "Could not calculate a median: calculateMedian requires a non-empty array"', () => {
+  expect(describeMedian([])).toEqual(
+    "Could not calculate a median: calculateMedian requires a non-empty array"
+  );
+});
+
+test('given something that isnt an array of numbers, returns "Could not calculate a median: calculateMedian requires an array of numbers"', () => {
+  expect(describeMedian("banana")).toEqual(
+    "Could not calculate a median: calculateMedian requires an array of numbers"
+  );
+});
diff --git a/Sprint-1/implement/max.js b/Sprint-1/implement/max.js
index 6dd76378e..886687cf6 100644
--- a/Sprint-1/implement/max.js
+++ b/Sprint-1/implement/max.js
@@ -1,4 +1,24 @@
 function findMax(elements) {
+  if (!Array.isArray(elements)) {
+    throw new Error("findMax requires an array of numbers");
+  }
+
+  if (elements.length === 0) {
+    return -Infinity;
+  }
+
+  if (
+    !elements.every(
+      (currentValue) =>
+        typeof currentValue === "number" && !Number.isNaN(currentValue)
+    )
+  ) {
+    throw new Error("findMax requires an array of numbers");
+  }
+
+  sortedElements = elements.toSorted((a, b) => a - b);
+
+  return sortedElements[sortedElements.length - 1];
 }
 
 module.exports = findMax;
diff --git a/Sprint-1/implement/max.test.js b/Sprint-1/implement/max.test.js
index ff3fbb5e5..ec46b1a71 100644
--- a/Sprint-1/implement/max.test.js
+++ b/Sprint-1/implement/max.test.js
@@ -12,32 +12,34 @@ We have set things up already so that this file can see your function from the o
 
 const findMax = require("./max.js");
 
-// Given an empty array
-// When passed to the max function
-// Then it should return -Infinity
-// Delete this test.todo and replace it with a test.
-test.todo("given an empty array, returns -Infinity");
-
-// Given an array with one number
-// When passed to the max function
-// Then it should return that number
-
-// Given an array with both positive and negative numbers
-// When passed to the max function
-// Then it should return the largest number overall
-
-// Given an array with just negative numbers
-// When passed to the max function
-// Then it should return the closest one to zero
-
-// Given an array with decimal numbers
-// When passed to the max function
-// Then it should return the largest decimal number
-
-// Given an array containing a value that isn't a number
-// When passed to the max function
-// Then it should throw Error("findMax requires an array of numbers")
-
-// Given something that isn't an array at all, such as "hey", 42 or no argument
-// When passed to the max function
-// Then it should throw Error("findMax requires an array of numbers")
+test("given an empty array, returns -Infinity", () => {
+  expect(findMax([])).toEqual(-Infinity);
+});
+
+test("given an array with one number, returns that number", () => {
+  expect(findMax([10])).toEqual(10);
+});
+
+test("given an array with positive and negative numbers, returns largest number overall", () => {
+  expect(findMax([10, 58, -74, 984, -87, -995, 47])).toEqual(984);
+});
+
+test("given an array with only negative numbers, returns number closest to zero", () => {
+  expect(findMax([-58, -65, -7, -2, -96, -753])).toEqual(-2);
+});
+
+test("given an array with decimal numbers, returns largest decimal number", () => {
+  expect(findMax([10, 9.5, 65.6, 41, 36.8])).toEqual(65.6);
+});
+
+test("given an array with with value that isn't a number, throws error", () => {
+  expect(() => findMax([10, 23, 18, "hello", 89, 2])).toThrow(
+    new Error("findMax requires an array of numbers")
+  );
+});
+
+test("given something that isn't an array, throws error", () => {
+  expect(() => findMax("Hello")).toThrow(
+    new Error("findMax requires an array of numbers")
+  );
+});
diff --git a/Sprint-1/implement/mean.js b/Sprint-1/implement/mean.js
index 36909ea1f..039c3507a 100644
--- a/Sprint-1/implement/mean.js
+++ b/Sprint-1/implement/mean.js
@@ -1,3 +1,29 @@
-function calculateMean(list) {}
+function calculateMean(list) {
+  if (!Array.isArray(list)) {
+    throw new Error("calculateMean requires an array of numbers");
+  }
+
+  if (list.length === 0) {
+    throw new Error("calculateMean requires a non-empty array");
+  }
+
+  if (
+    !list.every(
+      (currentValue) =>
+        typeof currentValue === "number" && !Number.isNaN(currentValue)
+    )
+  ) {
+    throw new Error("calculateMean requires an array of numbers");
+  }
+  
+  let total = 0;
+
+  for (number of list) {
+    total += number;
+  }
+  const mean = total / list.length;
+
+  return mean;
+}
 
 module.exports = calculateMean;
diff --git a/Sprint-1/implement/mean.test.js b/Sprint-1/implement/mean.test.js
index 847b88676..3cbf56a44 100644
--- a/Sprint-1/implement/mean.test.js
+++ b/Sprint-1/implement/mean.test.js
@@ -19,32 +19,38 @@ const calculateMean = require("./mean.js");
 
 // Acceptance criteria:
 
-// Given an array of numbers
-// When passed to calculateMean
-// Then it should return their mean
-// Delete this test.todo and replace it with a test.
-test.todo("given [1, 2, 6], returns 3");
-
-// Given an array with a single number
-// When passed to calculateMean
-// Then it should return that number
-
-// Given an array containing negative or decimal numbers
-// When passed to calculateMean
-// Then it should return the correct mean
-
-// Given an empty array
-// When passed to calculateMean
-// Then it should throw Error("calculateMean requires a non-empty array")
-
-// Given a value that isn't an array, e.g. "banana", 42, null or {}
-// When passed to calculateMean
-// Then it should throw Error("calculateMean requires an array of numbers")
-
-// Given no argument at all
-// When passed to calculateMean
-// Then it should throw Error("calculateMean requires an array of numbers")
-
-// Given an array containing a non-number value, e.g. [1, "2", 3]
-// When passed to calculateMean
-// Then it should throw Error("calculateMean requires an array of numbers")
+test("given [1, 2, 6], returns 3", () => {
+  expect(calculateMean([1, 2, 6])).toEqual(3);
+});
+
+test("given array with single number, return that number", () => {
+  expect(calculateMean([5])).toEqual(5);
+});
+
+test("given an array with positive and negative numbers, return the correct mean", () => {
+  expect(calculateMean([5, 8, -2, 7, -9])).toBeCloseTo(1.8);
+});
+
+test("given an empty array, throw an error", () => {
+  expect(() => calculateMean([])).toThrow(
+    "calculateMean requires a non-empty array"
+  );
+});
+
+test("given something that isn't an array, throw an error", () => {
+  expect(() => calculateMean("banana")).toThrow(
+    "calculateMean requires an array of numbers"
+  );
+});
+
+test("given no argument, throw an error", () => {
+  expect(() => calculateMean()).toThrow(
+    "calculateMean requires an array of numbers"
+  );
+});
+
+test("given an array with non-number values, throw an error", () => {
+  expect(() => calculateMean([1, 5, 9, "hello", 4])).toThrow(
+    "calculateMean requires an array of numbers"
+  );
+});
diff --git a/Sprint-1/implement/sum.js b/Sprint-1/implement/sum.js
index 9062aafe3..b7c76e9e3 100644
--- a/Sprint-1/implement/sum.js
+++ b/Sprint-1/implement/sum.js
@@ -1,4 +1,22 @@
 function sum(elements) {
+  if (!Array.isArray(elements)) {
+    throw new Error("sum requires an array of numbers");
+  }
+
+  if (
+    !elements.every(
+      (currentValue) =>
+        typeof currentValue === "number" && !Number.isNaN(currentValue)
+    )
+  ) {
+    throw new Error("sum requires an array of numbers");
+  }
+
+  let total = 0;
+  for (number of elements) {
+    total += number;
+  }
+  return total;
 }
 
 module.exports = sum;
diff --git a/Sprint-1/implement/sum.test.js b/Sprint-1/implement/sum.test.js
index a288e0f0a..a2cfb3389 100644
--- a/Sprint-1/implement/sum.test.js
+++ b/Sprint-1/implement/sum.test.js
@@ -10,27 +10,30 @@ const sum = require("./sum.js");
 
 // Acceptance Criteria:
 
-// Given an empty array
-// When passed to the sum function
-// Then it should return 0
-test.todo("given an empty array, returns 0")
-
-// Given an array with just one number
-// When passed to the sum function
-// Then it should return that number
-
-// Given an array containing negative numbers
-// When passed to the sum function
-// Then it should still return the correct total sum
-
-// Given an array with decimal/float numbers
-// When passed to the sum function
-// Then it should return the correct total sum
-
-// Given an array containing a value that isn't a number
-// When passed to the sum function
-// Then it should throw Error("sum requires an array of numbers")
-
-// Given something that isn't an array at all, such as "hey", 42 or no argument
-// When passed to the sum function
-// Then it should throw Error("sum requires an array of numbers")
+test("given an empty array, returns 0", () => {
+  expect(sum([])).toEqual(0);
+});
+
+test("given an array with one number, return that number", () => {
+  expect(sum([5])).toEqual(5);
+});
+
+test("given an array with negative numbers, correctly return sum of numbers", () => {
+  expect(sum([-10, -45, -6, -74])).toEqual(-135);
+});
+
+test("given an array with decimal numbers, correctly return total sum", () => {
+  expect(sum([12.7, 3.6, 32.48, 8, 32.53])).toEqual(89.31);
+});
+
+test("given an array with some values that aren't numbers, throw an Error", () => {
+  expect(() => {
+    sum([10, 8, 32, "hello", 2, 53, 32]);
+  }).toThrow(new Error("sum requires an array of numbers"));
+});
+
+test("given something that isn't an array, throw an Error", () => {
+  expect(() => {
+    sum("hello");
+  }).toThrow(new Error("sum requires an array of numbers"));
+});
diff --git a/Sprint-1/refactor/includes.js b/Sprint-1/refactor/includes.js
index 29dad81f0..916bcae13 100644
--- a/Sprint-1/refactor/includes.js
+++ b/Sprint-1/refactor/includes.js
@@ -1,8 +1,7 @@
 // Refactor the implementation of includes to use a for...of loop
 
 function includes(list, target) {
-  for (let index = 0; index < list.length; index++) {
-    const element = list[index];
+  for (element of list) {
     if (element === target) {
       return true;
     }