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A sample of college students reported they owned the following number of CDs. 52,76 ,64,79,80 ,74,66,69 1. What is the mean number of CDs owned?( ) 2. What is the median number of CDs owned?( ) 3. What is the range of the number of CDs owned?( ) 4. What is the sample variance of the number of CDs owned?( ) 1-4空直接填入数字,如2,10;且第4空的结果保留两位小数,如62.46.