In the Journal of Marketing Research (November 1996), Gupta studied the extent to which the purchase behavior of scanner panels is representative of overall brand preferences. A scanner panel is a sample of households whose purchase data are recorded when a magnetic identification card is presented at a store checkout. The table below gives peanut butter purchase data collected by the A. C. Nielson Company using a panel of 2,500 households in Sioux Falls, South Dakota. The data were collected over 102 weeks. The table also gives the market shares obtained by recording all peanut butter purchases at the same stores during the same period. Use the data given below: Brand Size Number of Purchases Market by Household Panel Shares Jif 18 oz. 3190.00 0.19 Jif 28 1839.00 0.07 Jif 40 754.00 0.05 Peter Pan 10 4078.00 0.16 Skippy 18 6299.00 0.26 Skippy 28 1621.00 0.13 Skippy 40 1472.00 0.14