The following table gives the scores of 30 students in a mathematics examination. Scores 90–99 80–89 70–79 60–69 50–59 Students
3 7 12 4 4 Find the mean and the standard deviation of the given data. Hint: Assume that all scores lying within a group interval take the middle value of that group. (Round your answers to two decimal places.)
The given data is Scores: 90-99 80-89 70-79 60-69 50-59 Students: 3 7 12 4 4 Because we are to take the middle value for each group. Therefore the total score is Sx = 3*94.5 + 7*84.5 + 12*74.5 + 4*64.5 + 4*54.5 = 2245 The number of students is 3+7+12+4+4 = 30
