Calculate statistic in EEPROM
Doing that calculation from EEPROM is exactly the same as doing it from any other source.  You have a count so you know where the EEPROM data ends.  You know where the EEPROM data starts.  You know how to read a number out of EEPROM.  What is stopping you from creating a for loop to read the i'th address from EEPROM and add all those numbers together just like you would for an array?

for (int i = EEPROM_START; i &lt; EEPROM_END; i++){
   sum = sum + EEPROM.read(i);
}
average = sum / count;


where EEPROM_START and EEPROM_END are supplied by you by knowing what address you started and ended writing at.