Recall that the main object in a boxplot is a box that is bounded by the first and the third quartiles. So the length of the box is the difference between the third and the first quartile, which is called the interquartile range. This is a measure of spread of the data; it is sometimes used as an alternative to the standard deviation If the data follow the normal curve, then the interquartile range equals how many standard deviations? (You may use the fact that the z-value of the third quartile is 0.7.)
a) 0.7
b) 1
c) 1.4
d) 2