diff --git a/tests/data/french_wilson/diagnostics.py b/tests/data/french_wilson/diagnostics.py
index e5f090ad..3f87aa6d 100644
--- a/tests/data/french_wilson/diagnostics.py
+++ b/tests/data/french_wilson/diagnostics.py
@@ -48,6 +48,13 @@
 plt.xlabel('Percent Error (J)')
 plt.savefig("J_hist.png")
 
+plt.figure()
+plt.hist((100.*(rs_F - F)/F)[~Centric], 100, color='k', label='Acentric', alpha=0.4)
+plt.hist((100.*(rs_F - F)/F)[Centric], 100, color='r', label='Centric', alpha=0.4)
+plt.legend()
+plt.xlabel('Percent Error (F)')
+plt.savefig("F_hist.png")
+
 plt.figure()
 plt.hist((100.*(rs_SigF - SigF)/SigF)[~Centric], 100, color='k', label='Acentric', alpha=0.4)
 plt.hist((100.*(rs_SigF - SigF)/SigF)[Centric], 100, color='r', label='Centric', alpha=0.4)