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.
One is that it's hard to see leaks in hidden areas such as a leaky evaporator inside the HVAC case. If you suspect an evaporator leak and dye has been added to the A/C system, you can check the evaporator case drain hose to see if any dye has gotten that far.The alternative is to spend several hours tearing apart the dash and HVAC system to visually inspect the evaporator for leaks.r, you could check the evaporator for leaks by simply inserting the probe of an electronic leak detector into the HVAC case. Dye also needs time to work. Once it has been added to an A/C system, it needs time to circulate with the refrigerant.