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2002 National Survey of Prices: Summary of Results (Small-scale outlet)
6 Price dispersion by item
- For some items such as women?s blouse, the price dispersion of small-scale outlets is larger than that of large-scale outlets, while for some food stuffs it is smaller.
- The price dispersion of convenience stores is significantly small, and particularly for some food stuffs.
(1) Concerning the common 100 items, looking at the price dispersion by an interquartile range which is standardized by an average price (see (reference)), for some clothing items (?women?s blouse?, ?women?s pants (100% wool)?, ?men?s pants?, etc.), ?cyclamen? and so on the price dispersion of overall small-scale outlets is larger than that of overall large-scale outlets. On the other hand, for some food stuffs such as ?retort-packed curry?, ?ice cream?, ?soy sauce?, ?instant noodles?, ?Cola?, etc. the price dispersion of overall small-scale outlets is smaller than that of overall large-scale outlets.
(2) Looking at the price dispersion of ?general retail outlet? and ?convenience store? which are the typical types of outlet among small-scale outlets, the price dispersion of ?convenience store? is significantly smaller than that of ?general retail outlet?, and particularly for food stuffs. Therefore, as shown in Chart 6.1, the price dispersion for items which are often sold at ?convenience store? appears to become small even for the overall small-scale outlets.
To study the differences of prices, not only average prices but also the distribution of the surveyed prices, in other words, "dispersion", is important. As one of the indicators to study this, there is an interquartile range.
The interquartile range means the values of prices located at three boundaries when the prices in the outlets surveyed are arranged in an order from the lowest to the highest and the total number of prices is divided equally into four groups, and these three values from the lowest are referred to as the 25th percentile point (the first quartile), the 50th percentile point (the second quartile or median (medium value)) and the 75th percentile point (the third quartile). The difference between the values of the 75th percentile point and the 25th percentile point is referred to as the interquartile range.
In addition, in order to facilitate a comparison of dispersion between items, the interquartile range is divided by the average price, and is standardized.