def test_pc_diff_from_mean_50pc(self):
"""Percentage difference from the mean between values where one is 50%
of the other"""
value_1 = 2000
value_2 = 4000
diff_1 = percentage_difference_from_mean(value_2, value_1)
diff_2 = percentage_difference_from_mean(value_1, value_2)
self.assertEquals(diff_1, diff_2)
self.assertAlmostEquals(0.333, diff_1, 2)
def test_pc_diff_from_mean_99pc(self):
"""Percentage difference from the mean between a very small value and a
relatively large value"""
value_1 = 0.0000000001
value_2 = 2**32
diff_1 = percentage_difference_from_mean(value_2, value_1)
diff_2 = percentage_difference_from_mean(value_1, value_2)
self.assertEquals(diff_1, diff_2)
self.assertAlmostEquals(0.999999, diff_1, 2)
def test_percentage_diff_from_mean(self):
"""Percentage difference from the mean between two values that are
almost equal"""
value_1 = 3999.9999
value_2 = 4000
diff_1 = percentage_difference_from_mean(value_2, value_1)
diff_2 = percentage_difference_from_mean(value_1, value_2)
self.assertEquals(diff_1, diff_2)
self.assertAlmostEquals(0.00000, diff_1, 2)
def _print_interval(self, output, percentage, interval, ingredient):
"""Output confidence interval for one ingredient"""
upper_value = percentage + interval
upper = self._float_format() % upper_value
lower_value = percentage - interval
lower = self._float_format() % lower_value
mean = self._float_format() % percentage
text = "The " + str(ingredient) + " proportion "
if interval == 0.0:
difference = 0.0
else:
difference = percentage_difference_from_mean(lower_value,
upper_value) * 100
if difference > 0.01:
diff_text = ("%% (the interval is %0.0f%% of the mean "
"proportion: %s%%)") % (difference, mean)
output.line(text + "is between " + lower + "% and " + upper \
+ diff_text)
else:
output.line(text + lower)
