Question

briefly explain loss of information in classified data

Answer 1

The classified data summarize the raw data making it more consise and comprehensive. It doesn't show the detail that are found in raw data.once the data are grouped into class an individual observation has no significance in further statistical data. Further, statistical calculation are based on the values of class mark, ignoring exact observation of data leading to problem of loss of information.

For example, the class 20-30contains 6 observation i.e., 25,25,20,22,25 & 28. So, when these data are grouped as class 20-30 in frequency distribution the latter provides only the number of records in that class (i.e., frequency=6) but not their actual values. Thus, use of class mark instead of actual values of observation in statistical method involves considerable loss of information.