A Comparison of Prices at Food City and Kroger • Justin A. Grieves, Byron H. Smith, Amy F. Szczepański, and Joseph R. H. White
Comparisons Made in Phase 3 • Grieves: various grocery items for price-conscious shopper (only collected unit price data) • Smith: beverage items • Szczepański: food items eligible for WIC • White: various grocery items
Primary Comparison: Logarithm of Price Ratio Logarithm of Kroger price / Food City Price Can conclude mean < 0 with p = 0.04 (t-test) Can conclude mean < 0 with p = 0.006 (Signed-Rank test)
Recommendations • Kroger is cheaper overall for shoppers who shop the entire store. • Kroger is cheaper for shoppers who are looking for the cheapest prices overall and do not care about whether the product is generic or not. • Wilcoxon Signed Rank Test: 95% confident that median price is between 0% and 5% less at Kroger.
Issue that Made a Difference Looking at a wide range of items made a difference. With beverages only, there was no statistically significant difference between the two stores. Wilcoxon Signed Rank: p = 0.5830
Finding Percentage Saved log ratio of items cheaper at Food City log ratio of items cheaper at Kroger BCa confidence interval BCa confidence interval 80.2% – 87.6% 83.3% – 90% Kroger price is 80.2% – 87.6% FC price FC price is 80.2% – 87.6% Kroger price Bootstrap used to find confidence interval for median.
Summary • Among our selected items, prices were on average cheaper at Kroger • Shop at Kroger if shopping for variety of items and don’t care about name brands. • Looking at a variety of items got statistically significant results when only beverages did not. • By shopping wisely at both stores, shoppers could save up to 17% – 20%.