How to do it...

The following code draws a histogram of experience data: 

1. Create a NumPy array with work experience (in years) of participants in a lateral training class:

grp_exp = np.array([12, 15, 13, 20, 19, 20, 11, 19, 11, 12, 19, 13, 12, 
                    10, 6, 19, 3, 1, 1, 0, 4, 4, 6, 5, 3, 7, 12, 7, 9, 
                    8, 12, 11, 11, 18, 19, 18, 19, 3, 6, 5, 6, 9, 11, 
                    10, 14, 14, 16, 17, 17, 19, 0, 2, 0, 3, 1, 4, 6, 
                    6, 8, 7, 7, 6, 7, 11, 11, 10, 11, 10, 13, 13, 15, 
                    18, 20, 19, 1, 10, 8, 16, 19, 19, 17, 16, 11, 1, 
                    10, 13, 15, 3, 8, 6, 9, 10, 15, 19, 2, 4, 5, 6, 9, 
                    11, 10, 9, 10, 9, 15, 16, 18, 13])

2. Plot the distribution of group experience:

nbins = 21 
n, bins, patches = plt.hist(grp_exp, bins = nbins)

3. Add axis labels and title for the plot:

plt.xlabel("Experience in years")
plt.ylabel("Frequency")
plt.title("Distribution of Experience in a Lateral Training 
           Program")

4. Draw the red vertical line in the graph at the average experience:

plt.axvline(x=grp_exp.mean(), linewidth=2, color = 'r') 

5. Display the plot on the screen:

plt.show()