Update app.py

app.py

@@ -742,9 +742,21 @@ elif st.session_state.current_index < len(st.session_state.data):
                 else:
                     st.session_state.step += 1
                     st.rerun()
+
 elif st.session_state.current_index == len(st.session_state.data):
     st.write(f"**Thank you for taking part in this study!** \n ")
-
+    c1, c2, c3 = st.columns([1,5,2])
+    step = st.session_state.step
+    with c1:
+        if st.button("<< Previous"):
+            if step > 0:
+                st.session_state.step -= 1
+                st.rerun()
+            else:
+                st.session_state.current_index -= 1
+                st.session_state.step = total_steps - 1
+                st.rerun()
+                
 if 0 <= st.session_state.current_index < len(st.session_state.data):
     st.write(f"Session {st.session_state.current_index + 1} out of {len(st.session_state.data)}")