Resolve "Refine answer statistics"

Closes #185 (closed)

src/app/components/shared/statistic/statistic.component.html

 <div fxLayout="column" fxLayoutAlign="center" fxLayoutGap="20px" fxFill>
   <div fxLayout="row" fxLayoutAlign="center">
     <mat-card>
-      <mat-card-header>
-        <h3>{{subject}}</h3>
-      </mat-card-header>
+        <div fxLayout="row" fxLayoutAlign="center">
+          <mat-card-title>
+            <h4>{{subject}}</h4>
+          </mat-card-title>
+          <button mat-raised-button>Show Correct</button>
+        </div>
       <mat-divider></mat-divider>
       <mat-toolbar></mat-toolbar>
       <div>