In volatile times for the stock market, investors need to know the best-positioned stocks in each sector for when they want to do some buying. That's why CNBC's Jim Cramer has been rolling out sector-by-sector power rankings, his selections of the top five most investable stocks in each market group based on their prospects. After tackling the communications services, consumer staples, consumer discretionary and energy spaces, the "Mad Money" host turned to health care. "If, like me, you're worried about a Fed-mandated slowdown, ... you absolutely need some health-care stocks in your portfolio. It's a terrific industry. This is a group of stocks that doesn't need a strong economy in order to thrive," Cramer said. "You don't stop taking medicine just because the economy slows down. Just like the consumer staples, the health-care names are as close as it gets to recession-proof." Here are Cramer's five favorite power players in the health-care space:

1. HCA Holdings Inc.

Cramer's favorite of the group was HCA Holdings, a for-profit health-care facility operator with a stock that has run 54 percent year to date. Calling HCA's stock "a steal" at its current $135.50 level, Cramer explained the thesis behind investing in HCA, which operates about 300 hospitals and surgery centers in densely populated and growing metropolitan areas. "These are areas where the consumer is feeling more affluent, and when people have more money in their pockets, they pay up for health care," he said. "Even though I'm worried about a Fed-mandated slowdown here, employment remains very strong and that's what matters for HCA, which is why the company had very strong volume growth this year, with patients getting more expensive procedures." Moreover, HCA has a good balance sheet and a smart management team, not to mention a potential political tailwind, Cramer said. "Just as Republicans are a party of tax cuts, Democrats are the party of spending more on health care," so a blue wave in November could be good news for HCA, he said. "Best of all, HCA is absurdly cheap. I can't believe, even after this run, [that] it sells for just 13.5 times next year's earnings estimates. The company reports in two weeks. I bet you'll like what HCA has to say."

2. Idexx Laboratories

Cramer's "humanization of pets" theory comes into full force with his second power play, veterinary diagnostics company Idexx Laboratories. "People are spending more and more money to keep their companion animals happy and healthy," the "Mad Money" host said, noting that shares of Idexx slipped 12 percent from their highs in the recent sell-off. "The fundamentals here remain very strong, and while the stock is still pretty pricey, that's because Idexx has a turbocharged growth rate," he continued. "The company reports on Nov. 1. I would pick some up before the report."

3. Intuitive Surgical

The medical devices stocks are some of the most resilient securities in the market, and niche device play Intuitive Surgical snagged third place in Cramer's health-care power ranking. "Intuitive Surgical occupies a very attractive niche here: their robotic-assisted surgery machines help doctors perform more procedures with better outcomes [and] fewer mishaps," Cramer explained. "In fact, the company practically invented this business with its da Vinci surgical system." What made Intuitive Surgical the "Mad Money" host's favorite robotic surgery play was its deeply ingrained razor-razorblade business model. The company sells the machine along with one-use items that it requires to function, "where the real money gets made," Cramer said. "Intuitive Surgical has the largest installed base of surgery systems — they have the most razors, so they sell the most blades," he explained. "This one reports Thursday night. Given the major pullback in the stock over the past week, I suggest putting on a small position before the quarter."

4. Centene

"Mad Money" regular Centene, a government-sponsored health insurer that gets business from Medicare and Medicaid, came in fourth. Cramer said Centene's $3.75 billion acquisition of Fidelis Care will give the company lasting growth prospects as it expands to new states and integrates Fidelis' systems. "The stock has been a spectacular long-term performer. I think it's got a lot more room to run," he said. "Centene knows what it's good at and they have expanded these offerings to cover as many people as possible. The company reports next Tuesday, and while I like it here, I would like it even more on a pullback, particularly a post-earnings pullback."

5. UnitedHealth Group

Last but not least on Cramer's power ranking for the health-care space was UnitedHealth Group, which the "Mad Money" host called "the best-run managed-care provider in America." "This is a stock that I've loved for ages," Cramer said, noting that his charitable trust owns shares. "But my favorite part of this business isn't even the insurance component. It's Optum, ... a division that's part pharmacy benefit manager and part provider of software, consulting and business practice outsourcing for the rest of the health care industry." Shares of UnitedHealth Group surged to a new 52-week high on Tuesday after the largest U.S. health insurer reported better-than-expected earnings and revenue for the third quarter. "I bet they're going to tell a very good story at their analyst day next month," Cramer said. "That's going to be another reason to own the stock. I hope the stock pulls back."

Final thoughts

Having some exposure to the health-care space — especially in shares of HCA, Idexx, Intuitive Surgical, Centene or UnitedHealth — might be a good bet for investors worried about the Fed's interest rate hike agenda, Cramer said. "The bottom line? You can't go wrong with some health care exposure here with the Fed going to squawk soon ... and talking about the three more hikes on top of December['s]," he concluded. "There's a lot working for you in this sector. I think it will keep working regardless of what happens with the broader economy."

WATCH: Cramer's power ranking for the health-care sector