UnitedHealth Group stock has been rallying on news that Berkshire Hathaway has invested in the business. Warren Buffett is the CEO of Berkshire Hathaway and the investment could be seen as a possible vote of confidence in UnitedHealth's business.

So while we should always try to assess where a stock or sector is headed, the better way to trade is with a simple framework: Any stock can go up and thus be a source of profits. However, owning each stock comes with different levels of risk,

Berkshire Hathaway has built up sizable investments in a handful of companies, according to a filing released on Thursday.