Update pages/5. Distributions.py

pages/5. Distributions.py

@@ -9,4 +9,7 @@ multi = """:green[Example:]Number of cars passing a red light
 - This could be 0, 1, 2, 3, or more cars.
 - The probability of each number would depend on factors like traffic volume and the timing of the red light.
 """
-st.markdown(multi)
+st.markdown(multi)
+
+st.subheader(":red[Probability mass function (PMF):]")
+st.write("A probability mass function (pmf) is a function over the sample space of a discrete random variable X which gives the probability that X is equal to a certain value. f(x)=P[X=x].")