8.15 The San Andreas Fault Geologists are inter- ested in shifts and movements of the earth's surface indicated by fractures (cracks) in the earth's crust. One of the most famous large fractures is the San Andreas fault in California. A geologist attempting to study the movement of the relative shifts in the earth's crust at a particular location found many fractures in the local rock structure. In an attempt to determine the mean angle of the breaks, she sampled n = 50 fractures and found the sample mean and standard deviation to be 39.8 and 17.2, respectively. Estimate the mean angular direction of the fractures and find the margin of error for your estimate.