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For a sample with a mean of M = 76 and n = 78, a score of X = 72 corresponds to z = -0.25. The sample standard deviation is s = O a. 18 O b. 25 O c. 16 O d. 20 A sample of n = 100 scores has a mean of 5. A second sample has n = 25 scores and M = 7. If the two samples are combined, the sample mean for the combined sample will be O a. Greater than 5 b. Equal to 4 O c. Less than 5 O d. Greater than 7