AngloGold Ashanti (NYSE: AU) could be a solid choice for investors given its recent upgrade to a Zacks Rank #1 (Strong Buy). This upgrade is essentially a reflection of an upward trend in earnings estimates — one of the most powerful forces impacting stock prices. The sole determinant of the Zacks rating is a company’s changing earnings picture. The Zacks Consensus Estimate — the consensus of EPS estimates from the sell-side analysts covering the stock — for the current and following years is tracked by the system. Individual investors often find it hard to make decisions based on rating up…