Points to Remember
• The information collected for a definite purpose is called data.
• The data collected by the investigator are known as primary data. When the information is gathered from an external source,the data are called secondary data.
• Initial data obtained through unorganized form are called Raw data.
• Mid Value = [ UCL + LCL ] /2 (where UCL–Upper Class Limit, LCL–Lower Class Limit).
• Size of the class interval = UCL – LCL.
• The mean for grouped data:
• The cumulative frequency of a class is the frequency obtained by adding the frequency of all up to the classes preceeding the given class.
• Formula to find the median for grouped data: Median =
• Formula to find the mode for grouped data: Mode =