diff --git a/app/controllers/collection_controller.rb b/app/controllers/collection_controller.rb
index ae6b698940..6a45e1a956 100644
--- a/app/controllers/collection_controller.rb
+++ b/app/controllers/collection_controller.rb
@@ -65,8 +65,12 @@ def user_contribution_list
   def approve_all
     @quality_sampling = QualitySampling.find(params[:quality_sampling_id])
     @pages = @collection.pages.where(status: Page::STATUS_NEEDS_REVIEW).where(:last_editor_user_id => @user.id)
+    page_count = @pages.count
     @pages.update_all(status: Page::STATUS_TRANSCRIBED)
-    flash[:notice] = t('.approved_n_pages', page_count: @pages.count)
+    @collection.works.each do |work|
+      work.work_statistic.recalculate({ type: Page::STATUS_NEEDS_REVIEW }) if work.work_statistic
+    end
+    flash[:notice] = t('.approved_n_pages', page_count: page_count)
     redirect_to(collection_quality_sampling_path(@collection.owner, @collection, @quality_sampling))
   end
 
diff --git a/app/helpers/quality_samplings_helper.rb b/app/helpers/quality_samplings_helper.rb
index b6388913dc..ccdacd69d4 100644
--- a/app/helpers/quality_samplings_helper.rb
+++ b/app/helpers/quality_samplings_helper.rb
@@ -7,7 +7,7 @@ def approval_delta_to_style(mean_approval_delta,max_approval_delta)
     "approval-delta approval-delta-#{approval_delta_to_quintile(mean_approval_delta,max_approval_delta)}"
   end
   def approval_delta_to_quintile(mean_approval_delta,max_approval_delta)
-    if max_approval_delta > 0
+    if max_approval_delta && max_approval_delta > 0
       ((mean_approval_delta / max_approval_delta)*4).round
     else
       0
diff --git a/app/views/quality_samplings/show.html.slim b/app/views/quality_samplings/show.html.slim
index ccfaa77971..2ba6a8abc9 100644
--- a/app/views/quality_samplings/show.html.slim
+++ b/app/views/quality_samplings/show.html.slim
@@ -31,8 +31,9 @@
             =pages_to_review
           -if page_sampling.reviewed_page_count > 0
             td.acenter
-              =(1.0 - @collection.pages.where(status: Page::COMPLETED_STATUSES).where(:last_editor_user_id => user.id).average(:approval_delta)).truncate(3)*100
-              span %
+             - approval_delta_average = @collection.pages.where(status: Page::COMPLETED_STATUSES).where(last_editor_user_id: user.id).average(:approval_delta)
+             = approval_delta_average ? (1.0 - approval_delta_average).truncate(3) * 100 : 0
+             span %
             td
               small(class="#{approval_delta_to_style(page_sampling.mean_approval_delta, @max_approval_delta)}") =approval_delta_to_display(page_sampling.mean_approval_delta, @max_approval_delta)
           -else