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2002 National Survey of Prices: Summary of Results (Large-scale outlet)
5 Price dispersion by item
- The price dispersion of clothing items is large, but among electric appliances, that of home audio-video equipment or personal computers is small.
(1) Looking at the price dispersion by an interquartile range which is standardized by the average prices (see (reference)), the price dispersion of clothing items is large, but among electric appliances, that of home audio-video equipment or personal computers is small. In addition, the price dispersion of food stuffs varies according to the items.
(2) Looking at the price dispersion of all of the surveyed 322 items by prefecture, that of Okinawa-ken is found to be the largest with 27 items which is the largest among all prefectures, while there are 17 items in Tottori-ken and 12 items in Yamagata-ken.
On the other hand, the price dispersion of Fukui-ken and Okinawa-ken is the smallest with 46 items, while there are 37 items in Wakayama-ken which is the smallest. (Items for which the nationwide dispersion is 0 are excluded.)
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.