I think it is human nature to over-editorialize a stocks movement immediately after an earnings report. We see Apple drops 3 percent and we think "Wall street is hammering them". Meanwhile another one of HN's favorite stocks, Tesla, has a larger percentage drop today with seemingly no major news and no one bats an eye. Such is the randomness of the stock market.
+/-3% is a common benchmark for the market's definition of "big swing". There's nothing really formal about it, and it's a more accurate measure when applied to the market as a whole rather than individual stocks. For a company like AAPL which is famous for not providing a lot of detailed information to investors, it might not be a big swing. For a different company, say P&G, it might be a huge swing.
Beta is one of many measures of volatility. Since it's a normalized correlation between the stock's rate of return and that of the market, it only really has meaning in the context of a stock's performance over a long time or in relation to the market as a whole. A stock's performance post-earnings is about as market-independent as you can get, however.
I'd add that it's colloquial. When a stock drops it's "getting hammered". Also, after hours is deceiving. NFLX was up 50pts after hours with their last earnings announcement. It dropped 80pts the next day.
Doesn't sound like it when looking at the percentage. Apple had a market capitalization of $481,390,000,000 at the market close today. So 3% of that is $14,441,700,000. Seems more significant in whole numbers.
The real thing to consider is that every stock is much more thinly traded in after markets than it is during regular hours. For that reason, the few people trading during that time are typically not representative of the entire investment community.
After Hours trading is volatile and not terribly important. Just last week you saw Netflix soar in AH trading and plummet almost instantly on open.
A 3% price move is nothing noteworthy, especially in AH trading. IMO the only seasoned way to view this is that the judgement of the markets of this ER is still pending.
Sept 16
Sept 10
Sept 20
EDIT "5 second" was to emphasize I could be wrong, not to be a dick.