Chi Squared Test

chi.py

# chi_square_test : [(number, number)] -> number
# consumes a list of tuples containing the observed data and expected data
# produces the chi squared term of the dataset
def chi_square_test(data_points):
    s = 0
    for point in data_points:
        o, e = point
        s += (o - e)**2/float(e)
    return s

# is_significant : number number -> boolean
# determines if a chi squared term is significant based on the degrees of freedom
# uses 95% confidence as the threshold
def is_significant(chi_term, degrees_of_freedom):
    threshes = [3.841, 5.991, 7.815, 9.488, 11.070, 12.592, 14.067, 15.507, 16.919, 18.307, 19.675, 21.026, 22.362, 23.685, 24.996]
    return chi_term >= threshes[degrees_of_freedom + 1]