Splits and dividends should be factored into the price. I use the adjusted closing price http://www.investopedia.com/terms/a/adjusted_closing_price.a....

However in this case with Ebay it wasn't a stock split but rather a big chunk of Ebay (Paypal) split off into a separate independent company. I think what happened is when Ebay and Paypal separated Ebay share owners gained the equivalent Paypal shares. So this would throw off the numbers.