Researchers randomly assigned 25 beginning students of Russian to begin speaking practice immediately and another 25 to delay speaking for 4 weeks. At the end of the semester both groups took a standard test of comprehension of spoken Russian. Suppose the test scores for early speaking vary according to the N(35, 8) distribution and scores for delayed speaking have the N(31, 6) distribution. What is the sampling distribution of the mean score x in the early speaking group in many repetitions of the experiment?