10 households, e.g. type/size of dwelling, ownership of vehiclcs, number/type of appliances, neighborhood, etc. With spatial stratification, use of functional rather than administrative regions may be more appropriate when trying to link consumption patterns with ecological zones. However, it may be difficult to stray too far from official administrative division, as many statistics are only available on this basis. Finally, it should be noted that the more a sample is stratified, the more it requires a larger sample to ensure that results obtained from the sample are generalizable to the larger population Sample Size Should Be Calculated. When using random survey techniques, the sample size should be calculated using statistical methods which determine sampling error and confidence level. However, if resource constraints limit the sample size, then its reliability and precision should be determined by working backwards from the feasible sample. Confidence levels and sampling error should always be given to clarify the validity of published results. Simply selecting a sample based on 1% or 0.1% of the population does not guarantee that results will be representative.

# Sample Design in Morocco

A household energy consumption survey has been designed in Morocco under a USAID/ESMAP project. It will involve three rounds to capture winter, spring, summer and crop-related seasonality. The objective of the survey is to provide data to analysts on fuelwood developmcnt, household energy conservation, cooking equipment, fuel prices, petroleum products and rural electrification so that a comprehensive household energy strategy can be developed.

Sampling methodology. A random stratified sample was drawn from the Statistics Departmen.'s master sample. This is a large sample which is designed to meet all household survey needs for the 1984-92 period. It is based on the 1982 census and is already divided into rural and urban areas, and five strata refleciing housing types. Sampling involved the following phases: (a) review of existing data; (b) selection of zones to be surveyed; (c) familiarization with the master sample; (d) selection of sampling procedure and estimation of the size, reliability and precision of the sample; (e) distribution of the sample in time and space; and (f) selection of the method for estimating population parameters from the sample variables.

Sttatification. Stratification aimed at capturing geographical factors such as proximity to the forest, the structure of urban vs. rural demand and socioeconomic factors affecting consumption. Administrative districts were not suited to this stratification so the country was divided into four survey zones according to energy, forest and climate characteristics. Each zone included several administrative provinces and the criteria used for grouping provinces into zones were: electricity consumption; rate of LPG use; forest surface; minimum temperature in winter; and rainfall recorded by the nearest meteorological station.

Sample size. Because of the selection and stratification techniques used, a sample size of 6080 households was chosen (2800 rural and 3280 urban) at a 95% confidence level. If a lesser degree of precision and stratification was desired, the sample could have been as small as 2200 households. The sample size will be the same for each round. To minimize biases, a portion of the households visited during the first -ound will be visited during the second, and a portion of the second will be visited during the third. The duration of the survey will be approximately three weeks in each round.