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NEW YORK (TheStreet) -- If you can't do your own homework, go buy an index fund. That was Jim Cramer's advice to his Mad Money viewers Wednesday after billionaire Warren Buffett's latest trades became public, sending a multitude of stocks higher.

"Don't be a lemming. Do your own homework and make up your own mind," Cramer urged investors. If you don't have the time or inclination for homework, Cramer said there are plenty of great index funds, including S&P 500 and dividend funds, that make terrific investments you can just own and not worry about.

So what's wrong with following famous money managers like Buffett? First off, Cramer said, the filings released today are already months old, making them virtually useless. Second, since we never learn why Buffett likes a stock we'll never know when to sell it. Third, Buffett is under no obligation to tell us when he's cashing out of a position.

For example, shares of IBM (IBM - Get Report)  shot up today on news that Buffett is a buyer. But IBM also has an analyst day scheduled for next week, which will likely once again bring to light how the company is struggling to deliver the growth it promised.

Then there's John Deere (DE - Get Report) , another Buffett holding that rose on the day. Cramer said Deere reports its earnings on Friday and almost always sees its shares tank after it reports. Those investors who bought Deere today blindly are likely in for a rude awakening later this week.

Cramer said if investors have any hope of making money in today's markets, they shouldn't rely on him or Buffett or a company's CEO or anyone else, for that matter. You need to rely on yourself, he concluded. Do your own research and know what you own and why.

Executive Decision: Walter Robb

For his "Executive Decision" segment, Cramer spoke with Walter Robb, co-CEO of Whole Foods Markets (WFM) , which last week announced an earnings beat on a 10.2% rise in revenue while reaffirming full-year guidance.

Robb said today's consumer cares where their food comes from and what happens to it along the way, which is why Whole Foods' message of quality and transparency is resonating more and more. He said this caring even extends beyond their customers, as team members also are clamoring to work for a company that shares their values.

But beyond healthy food, Robb noted that Whole Foods is also a technology story. The company is now the number one retailer using Apply Pay and the Instacart food delivery service. Robb said customers need to be at the center of the retail universe; at Whole Foods, they are.

Turning to the topic of competition, Robb said competition only makes the company better because it allowed his company to differentiate itself even more, leading to broad-based momentum.

Cramer said Whole Foods remains a terrific growth story.

What's Brewing at Starbucks

There are many reasons to own shares of Starbucks ( SBUX - Get Report) , Cramer told viewers, but the price of coffee beans shouldn't be one of them.

Cramer, whose charitable trust, Action Alerts PLUS, holds Starbucks, said after listening to the latest conference call it's clear the company is firing on all cylinders, with the coffees, teas, packaged goods, stores and technology programs all performing better than expected. So why are investors fretting over the price of coffee beans?

Last year's rise in coffee prices spooked many investors, causing hedge funds to short the stock like crazy, Cramer told viewers. But in the end, CEO Howard Schultz said coffee prices wouldn't be an issue, and they weren't.

But fast forward to today, when prices are at one-year lows. Investors still don't seem to have gotten that message. Wake up and smell the coffee, Cramer quipped, Starbucks is about the experience, the personal service, the "third place" to gather outside of home and office.

Starbucks has never been about the price of coffee, Cramer concluded, which he why he continues to recommend that investors must own the stock for the long term.

Executive Decision: Jim Reid-Anderson

In his second "Executive Decision" segment, Cramer sat down with Jim Reid-Anderson, chairman and CEO of amusement park operator Six Flags (SIX - Get Report) , which today posted a 19% rise in revenue on a 15% increase in attendance at its theme parks in the wake of lower gasoline prices.

Reid-Anderson said Six Flags remains committed to innovation in all forms, whether it's new rides, new ways to enjoy its parks or new technologies. He said that 2015 is shaping up to be the best line-up of new rides in the company's 54-year history, but he's also excited about other innovations.

Two of those new innovations include biometric scanning at the gate, so season pass holders no longer have to carry their cards with them, and Six Flags new All-Season Dining Pass, which allows guests to enjoy two meals a day, all season long.

In addition to innovation, Six Flags is also committed to driving cash flow and returning cash to shareholders, Reid-Anderson said. Over the past four years, his company has returned $1.5 billion and will continue to increase its dividend and buy back shares.

Cramer said few companies offer both growth and yield, but Six Flags is one of them.

Lightning Round

In the Lightning Round, Cramer was bullish on Schlumberger (SLB - Get Report) , Acorda Therapeutics (ACOR - Get Report) , MGM Resorts (MGM - Get Report) , Oaktree Capital Group (OAK - Get Report) and Dominion Resources (D - Get Report) .

Cramer was bearish on Las Vegas Sands (LVS - Get Report) , B&G Foods (BGS - Get Report) , Marketo (MKTO) , GoPro (GPRO - Get Report) and NextEra Energy (NEE - Get Report) .

Am I Diversified?

In the "Am I Diversified?" segment, Cramer spoke with callers and responded to tweets sent via Twitter to @JimCramer to see if investors' portfolios have what it takes for today's markets.

The first portfolio included Iron Mountain (IRM - Get Report) , Apple (AAPL - Get Report) , AT&T (T - Get Report) , ConEd (ED - Get Report) , Yahoo! (YHOO) and Walt Disney (DIS - Get Report) .

Cramer said this portfolio needs to trade in Yahoo! for a drug stock like Bristol-Myers Squibb (BMY - Get Report) .

The second portfolio's top holdings included Apple, Alibaba (BABA - Get Report) , Icahn Enterprises (IEP - Get Report) , DineEquity (DIN - Get Report) and Waste Management (WM - Get Report) .

Cramer blessed this portfolio as properly diversified.

The third portfolio had Panera Bread (PNRA) , UPS (UPS - Get Report) , Bank of America (BAC - Get Report) , Royal Dutch Shell (RDS.A - Get Report) and Regeneron (REGN - Get Report) as its top five stocks.

Cramer also said this portfolio was the definition of diversification.

The fourth portfolio's top stocks were Amgen (AMGN - Get Report) , Costco (COST - Get Report) , Google (GOOGL - Get Report) , Wal-Mart (WMT - Get Report) and Celgene (CELG - Get Report) .

Cramer advised selling both Amgen and Wal-Mart and adding United Technologies (UTX - Get Report) and Royal Dutch Shell.


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-- Written by Scott Rutt in Washington, D.C.

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At the time of publication, Cramer's Action Alerts PLUS had a position in AAPL, GOOGL, RDS.A, SBUX, UPS and UTX.