We have three measurements of the value of a parameter made with the same instrument, x = 5.77,5.78,5.75, and three measurements of the value of another parameter made with three different instruments whose instrumental precision is well known: y = 5.68 0.12, 5.73 0.15, 5.631 0.070. Find = x - y, its error, and its 68% confidence interval. Why is 68% often used for confidence * intervals?