A quality control manager at the Don Mills Electronics Company knows that his company has been making surge protectors with a 10% rate of defective units. He has instituted several measures designed to lower that defect rate. In a test of 20 randomly selected surge protectors, only one is found to be defective. If the 10% defect rate hasn't changed, find the probability that among 20 units, 1 or none is defective. Based on the result, does it appear that the newly instituted measures are effective?