U.S. stocks slumped, with the Standard & Poor’s 500 Index falling below its 200-day average, as investors weighed prospects for Federal Reserve interest rate increases and slowing global economic growth.

Welcome to edition 217 of Insider Weekends. Insider buying decreased significantly last week with insiders buying $33.73 million of stock compared to $113.26 million in the week prior.

For former drug researcher Raghuram "Ram" Selvaraju, picking biotech stocks is both science and art. It's about understanding the competitive landscape and the mechanisms of drug action, and then making sure all the pieces fit together for a plausible investment case.

Our weekly best and worst reports show you stocks with the best (and worst) potential returns over the coming 6 to 12 months.