First of all, it's all about statistics, so of course you have to think statistically. The first step is to study what light bulbs are most relevant to, naturally, households and businesses. So to find households and businesses as a sample, first get the total number of businesses and households in the region, the simplest is to randomly select a certain number of this minimum number is determined by the statistical formula, up to no more than 2,000 households. Of course, it is also possible to study the relationship between the number of light bulbs and the number of households and businesses before choosing a sampling strategy. These things a person to deal with, the remaining nine people are in accordance with your sample size to go to the door to visit each household to count each household light bulbs. Finally, the results are counted.