13 Stocks Moving In Tuesday's After-Hours Session

Gainers

• Akamai Technologies, Inc. AKAM shares were up 11 percent after hours, following a third-quarter earnings and sales beat. Q3 EPS came in at 62 cents, topping estimates by 3 cents. Sales were $10 million higher than estimates at $621 million.
• iRobot Corporation IRBT moved 6 percent higher, with Q3 adjusted EPS coming in 5 cents higher than estimates at 52 cents.
• Regal Entertainment Group RGC gained 4 percent after delivering a third-quarter earnings and sales beat.
• Illumina, Inc. ILMN shares were up about 1 percent after reporting a third-quarter earnings and sales beat. Q3 adjusted EPS came in at $1.11, beating estimates by 12 cents. Sales were $21 million higher than estimates at $714 million.
• Weibo Corp (ADR) WB shares were highly volatile in the after-hours session.

Losers

• Savara inc SVRA dropped over 12 percent after announcing a proposed public offering of common stock.
• Advanced Micro Devices, Inc. AMD dropped 11 percent despite a third-quarter earnings beat. While AMD beat both top and bottom line estimates, the company forecasts a 12-18 percent drop in sales in Q4.
• Chipotle Mexican Grill, Inc CMG plummeted 10 percent, after delivering third-quarter earnings far below estimates.
• Juniper Networks, Inc. JNPR shares fell nearly 7 percent after posting earnings that fell in line with analyst estimates. The company forecasts fourth-quarter earnings well short of expectations.
• Edwards Lifesciences Corp EW shares fell 6 percent. Q3 sales came in $10 million short of estimates.
• AT&T Inc. T shares of the telecom giant moved down nearly 2 percent, after missing third-quarter earnings estimates.
• Express Scripts Holding Co ESRX shares were down about 1 percent following earnings.
• Texas Instruments Incorporated TXN was down about 1.4 percent.

After-hours price action occurs in an environment where fewer traders are participating in price discovery. Amid this lack of activity and liquidity in certain stocks, experienced traders will sometimes attempt to manipulate sentiment by placing an order at a price markedly different than a stock's closing price or last price.

It's conceivable less savvy investors could see this price action, assume the sharply higher or lower indication is a signal of news, buy or sell the stock, and ask questions later. This is one reason after-hours price action can sometimes evaporate by the next day's morning trading session (i.e. there is no news -- just trading activity).