A confidence interval is a range of possible values for the
experiment objective you are trying to measure.
Attributes:
confidence_level (float):
The confidence level used to construct the
interval, i.e. there is X% chance that the true
value is within this interval.
ratio (float):
The percent change between an experiment
metric's value and the value for its control.
lower_bound (float):
Lower bound of the interval.
upper_bound (float):
Upper bound of the interval.