change of statistics

src/components/courses/all/CourseCard.vue

@@ -153,6 +153,7 @@ import useCourseCard from "@/composables/courses/all/useCourseCard";
 import AvatarContainer from "@/components/users/profile/AvatarContainer";
 import { judgeItems, instituteInfo, scoreInfo } from "@/composables/global/useStaticData";
 import { averageOf } from "@/composables/global/useArrayUtils";
+import { bayesianAverageOf } from "@/composables/global/useArrayUtils";
 import { roundScore, enoughDataThreshold } from "@/composables/global/useParseScore"
 
 export default {
@@ -184,7 +185,14 @@ export default {
       let rounded = roundScore(score, this.course["comment_num"]);
       this.roundedScore.push(rounded);
     }
-    this.averageScore = averageOf(this.course.score) * 20;
+    // Bayes statistics inference
+    // averageScore = (C * m + Σ(ratings)) / (C + N)
+    // C: Prior Comments Count = 2
+    // m: Prior Mean Rating = 3.19
+    // N: Current Comments Count = this.course.score
+    // By the way, we set a bar that the course must have at least 8 comments
+    // and the raw average score at 5 to consider this course as a full score course. 
+    this.averageScore = bayesianAverageOf(this.course.score, 4.1, 1, 5) * 20;
   },
 };
 </script>

src/composables/global/useArrayUtils.js

@@ -36,6 +36,25 @@ export function averageOf(arr) {
   return sumOf(arr) / arr.length
 }
 
+/**
+ * Given an array, an prior average and prior count, return the bayesian average of those items.
+ * @param {Array<any>} arr
+ * @param {Array<any>} priorAverage
+ * @param {any} priorCount
+ * @param {any} fullScoreBar - The number of reviews required to consider the average as 5.
+ * @returns any - The bayesian average of the numbers in the array.
+ */
+export function bayesianAverageOf(arr, priorAverage, priorCount, fullScoreBar) {
+  if (arr.length == 0) {
+    return 0;
+  }
+  if(averageOf(arr) == 5 && arr.length >= fullScoreBar) {
+    return 5;
+  }
+
+  return (priorCount * priorAverage + sumOf(arr)) / (priorCount + arr.length)
+}
+
 
 /**
  * It takes an array of numbers and returns an array of numbers that are the same proportions of the