Shares of Amazon.com Inc. AMZN, -4.06% sank 4.6% in afternoon trading, and has now lost 8.6% in two days, as investors prepped for the ecommerce giant’s third-quarter results after the closing bell. The stock has declined the day after results were reported 6 times in the last 8 quarters, with an average decline of 5.1% and an average gain of 12.0%; the average one-day post-earnings move in either direction was 6.9%. A stock options strategy known as a straddle, in which both bullish (calls) and bearish (puts) options with strike prices at current levels, with Friday expiry, were priced for a $8.71 price move in either direction on Friday, according to data provided by Matt Amberson, principal at Option Research & Technology Services (ORATS). Based on current prices, that means buyers of a straddle will be in the money if the stock moves 7.9% in either direction on Friday. Amazon’s stock has tumbled 33.9% year to date, while the SPDR Consumer Discretionary Select Sector ETF XLY, -0.39% has shed 29.3% and the S&P 500 SPX, -0.60% has lost 20.0%.