I have price data for similar products in different stores like below
productId StoreA StoreB StoreC StoreD
00001 14 10 14 15
00002 35 34 36 40
00003 100 94 90 94
00004 14 14 25 14
00005 11 15 13 10
StoreA is my base store to which I want to compare other store's prices. Currently my approaches are naive.
Approach 1: Calculating %change = (storeA/AVERAGE(storeB, storeC, storeD))-1 # MEAN is sensitive to outliers so in ID 00004 all prices are same in all stores except storeC so overall I am not getting correct metric/index which represents the data
Approach 2: Calculating variance = ((storeA - storeB)**2+(storeA - storeC)**2+(storeA - storeD)**2)/3 # Here storeA is my base store so I am taking it as mean price
Any better approaches to get a single index for comparing prices with a base price ?