Sony Pictures Home Entertainment apparently wants to see whether withholding DVD titles from Netflix for 28 days will boost sales. It said Wednesday that it plans to release some DVDs to the online rental company on the same day they hit retailers and others four weeks later. The first movie being delayed is The Karate Kid , which was released on DVD on Tuesday. In September Disney chief Robert Iger said that other studios persuaded Netflix (and kiosk operator Redbox) to delay renting DVDs for 28 days by offering them 50-percent discounts on the discs. "[That] was not an equation that made sense to us," he said. Although Netflix does not disclose the number of DVDs it buys, some estimates put the number at an average of 100,000 to 200,000.