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In surveys of ambient gamma dose rates covering a large area,the measurements in individual locations are usually performed for a short duration since a large number of locations need to be covered within a given time frame.It is common to record a few readings (usually about 3-5 readings depending upon the type of instrument used) for a short time interval using a gamma dosimeter and the average value is taken as the representative value for the location under investigation.In this work,an approach is presented in which it is possible to determine the minimum number of readings that would be adequate enough to provide a mean average value with a desired accuracy (10% relative error at a confidence level of 95%).Using a GM-dosimeter,a number of data sets on ambient gamma dose rates were collected in different indoor locations for two different sampling intervals of 10 minutes and I hour.The measurements made over a period of one-day are considered to be long enough to provide a good representative value for the dose rate in the investigated location and also are expected to have reduced effects of diurnal variations in the gamma dose rate.The measurements carried out under this work covered a wide range of dose rates,from about 30 nSv/h t0 190 nSv/h.The lower dose values in this range were obtained by placing the dosimeter inside a lead shield and the higher values by using radioactive sources.Student t-test was performed on data sets which contained different number of measurements (data points) for the lO-min interval sets (3-144 measurements) and for l-hour interval sets (2- 24 measurements),to check their relative deviations with respect to their means.The analysis shows that for low dose rate levels,more repeated measurements are required for improved accuracy.More importantly,it takes fewer readings for the l-hour interval measurements to achieve the desired accuracy compared to that of the lO-min interval.But,such situations require longer times for the field measurements.For example,rather than spending 4 hours in a location to perform a study using measurements of l-hour interval,the lO-min interval would provide a similar accuracy (of 10%) within 2 hours (12 readings of lO-min each) for dose rate levels of typical values of indoor measurements.