In "Ch2_MorePyMC_PyMC3" under "Including observations in the Model" section

[doh-wrong-button]

This fixes 'normed' (which is deprecated) to 'density'. PS: I am a complete nooooob. If this is incorrect, I apologize. It worked for me :)....Thanks, signed your loving son, Homer

%matplotlib inline
from IPython.core.pylabtools import figsize
import matplotlib.pyplot as plt
import scipy.stats as stats
figsize(12.5, 4)

samples = lambda_1.random(size=20000)
#plt.hist(samples, bins=70, normed=True, histtype="stepfilled") normed is deprecated (old #code)
#density performs the same as normed (new code below)
plt.hist(samples, bins=70, density=True, histtype="stepfilled")
plt.title("Prior distribution for $\lambda_1$")
plt.xlim(0, 8);