These values have mean of 17 and standard deviation of about 4.1. If instead we first calculate the range of our data as 25 â 12 = 13, and then divide this number by four we have our estimate of the standard deviation as 13/4 = 3.25.
Plastic marked with an SPI code of 4 is made with low-density polyethylene, or LDPE. LDPE is not commonly recycled, but it is recyclable in certain areas. It tends to be both durable and flexible. It isn't known to release harmful chemicals into objects in contact with it, making it a safe choice for food storage.
Other types of topical sealers for driveways are polyurethanes, epoxies and penetrating resins. Generally, epoxy or polyurethane sealers cost considerably more than acrylics and they tend to be higher build, and thus more slippery. They also don't allow for moisture vapor to move out of the concrete.