Installation instructions:

1. Install Python 3.7.0 if necessary.
2. Create a new Python virtual environment named 've' in the 'chapter_13_examples' directory:
   $ python3 -m venv ve
3. Activate the virtual environment:
   $ source ve/bin/activate
4. Upgrade pip:
   (ve)$ pip install --upgrade pip
5. Install required packages:
   (ve)$ pip install -r requirements.txt

Instructions for running scripts:

1. Activate the virtual environment:
   $ source ve/bin/activate
2. Run the desired scripts:
   (ve)$ python example_13_1.py
(ve)$ python figure_13_1.py --confidence_intervals
(ve)$ python figure_13_2.py --confidence_intervals
3. Deactivate the virtual environment when finished:
   (ve)$ deactivate