What is really needed is the distance from each grade to the mean not the difference. You could take the absolute value of each difference and then calculate the mean. This is called the mean deviation, i.e. mean deviation = , where n is the number of students in the class. For class 1 this is 64/5 = 12.8.
1. Determine if there is a roof leak. Look for mold or mildew in attics or on walls. Look for discoloration on ceiling tiles or drywall. Look for wet, moist and rotting wood in crawl spaces, around chimneys or other additions, such as skylights and vents.. Check the attic for dyed areas. Follow the dye path from where it begins to where it comes out to find the leak. There may be multiple points of entry, so if you find one point, continue to search thoroughly until you are satisfied that there are no more leaks.
Instructions. Inspect the attic with the flashlight for any signs of leaks. Leaks can be identified by stains on the wood framing that makes up the roof structure, brown or gray discoloration, or black mold growth or black stains in a vertical line.Trace the darkest of the stains up to the metal roof itself.Chances are the leak is caused by an unsecured roof fastener such as a screw or nail.etal roofs on your home and outbuildings protect not only the belongings stored in them, but also the structure itself. Finding the source of a leak immediately is crucial to keeping the wooden frame of the structure from rotting. Inspect both the interior and the exterior of the roof if necessary to find the leak. 1  Flashlight. 2  Hammer.