Significant increases were made in Chevron, Constellation Brands, Domino’s Pizza, Pool Corp, and Heico, reflecting Buffett’s conviction in these holdings.

Shares of UnitedHealth Group are surging before the market open Friday as Warren Buffett’s Berkshire Hathaway disclosed that it recently purchased shares of the beleaguered insurer.

While this confirms our earlier evaluation that the stock seems attractively priced, the underlying operational challenges still exist—medical cost ratios sitting at 89.4%, compressed profit margins,...