We can’t guarantee positive outcomes, she says, but, “We can increase the odds that things will work out.”

How so?

Start by defining your goal, she says. Then ask, “How can you achieve your goal with no risk at all, or as little risk as possible?”

For example, let’s say you want to figure out how much money you need for retirement. If you use her framework, she suggests you may discover that traditional approaches are riskier than you might have thought.

One such approach is to invest as much as you can, and, once you retire, draw out a fixed amount annually. A common rule of thumb is to withdraw 4 percent of your portfolio each year. But if you follow that rule strictly, the dollar amount of that annual 4 percent withdrawal will vary, depending on the performance of your portfolio.

“That’s where the strategy goes wrong,” she says. “A predictable salary, like the one you earned when you were working, should be the goal of your retirement fund. Most workers wouldn’t accept a salary that varies with stock prices — why should retirees?”

You can gain certainty by buying a fixed annuity. That requires you to hand over some, or all, of your money to an investment firm in exchange for guaranteed payouts.

All of this is worth thinking about, but if you want to know what you should do, there is no answer here. The problem, in this case, is that Ms. Schrager doesn’t make a recommendation to buy annuities, nor does she come out against them. That kind of fuzziness, when it comes to practical recommendations, is a flaw in the book.