4. It has long been known that learning large amounts of new information over a period of time (i.e., distributed learning} often results in better retention of that material than learning the material all at one time (i.e., massed learning). To demonstrate this phenomenon to his students, Balch (2006) conducted a study where students were asked to use massed learning or distributed learning to learn a list of words. Sup- pose the following study was done. Twenty-four students were selected for a study where they were asked to learn a list of words. The students were randomly assigned to two groups of [2 students each, a distributed learning group and a massed learn- ing group. Each group heard the same list of words twice, however, the massed learning group heard each word back-to-back, whereas the distributed learning group heard each word twice, but in a random order. Following a delay, the stu- dents' memory for the list of words was tested. The number of words recalled for each group is listed below. Learning Condition Distributed (x1) Massed (x2) '3' 6 s 5 6 6 7 2 5 7 7 4 s 7 7 4 5 6 7 7 s 6 9 6 a. What type of research design, between-subjects or within-subjects, was used in this study? b. Find the mean and standard deviation for each treatment condition. Then use a t test to answer the question: Does distributed learning lead to better retention of a list of words than massed learning? Use a two-tailed test and a .05 significance level. 0. What is the value of 112 for this study? What proportion of the variance in the dependent variable can be accounted for by knowing the level of the independent variable? d. Find the 95 percent confidence interval for the difference between the two popula- tion means. 9. Describe your results following the example illustrated in the Reporting the Results of a tTest section of this chapter