Horseradish Dill Potato Salad

In a microwave-safe bowl combine the potatoes, cut into 1-inch pieces, and the water and microwave the potatoes, covered with microwave-safe plastic wrap, at high power (100%) for 6 to 8 minutes, or until they are tender. Let the potatoes stand, covered, for 3 minutes, drain them, and let them cool completely. In a bowl whisk together the mayonnaise, the yogurt, the mustard, the vinegar, the horseradish, the dill and salt and pepper to taste, add the carrot, the onion, and the potatoes, and toss the salad until it is combined well.