An Error Bar is a means by which the accuracy of observations or calculations can be expressed. It consists of a line segment crossing a point or the top of a bar graph showing a range of values around the indicated value. It indicates that the point is only the most probable value, and its length usually indicates one standard deviation of the variance or confidence level. It generally indicates there is a 95% chance of the value being somewhere along the length of the bar. This is the normally expected interpretation, but a graph may outline an alternative meaning.