def evaluate_PDF(rv, x=4):
    """Input: a random variable object, standard deviation
    output : x and y values for the normal distribution
    """
    import numpy as np
    import scipy.stats as stats
    import scipy
    mean = rv.mean()
    std = rv.std()
    xs = np.linspace(mean - x * std, mean + x * std, 100)
    ys = rv.pdf(xs)
    return xs, ys
