ISO 8243:2013 specifies two methods of providing representative samples of a population of cigarettes manufactured for sale. Different procedures are specified according to whether sampling is undertaken at the point of sale or at a factory. Sampling "at one point in time" provides for appraisal of the chosen properties of the cigarettes on that occasion. Sampling is carried out within as short a period as possible. Sampling "over a period of time" provides for on-going appraisals. It can be considered for practical purposes as a series of samples each taken "at one point in time". ISO 8243:2013 provides information on the statistical basis for the treatment of data and gives estimates, based on practical experience, of the typical confidence intervals for nicotine-free dry particulate matter (NFDPM), nicotine and CO yields which may be found when a product is sampled in accordance with ISO 8243:2013 and smoked in accordance with the procedures specified in ISO 3308, ISO 3402, ISO 4387, ISO 8454, ISO 10315, ISO 10362‑1 and ISO 10362‑2.