Lynette received her bank statement for the month and she is now comparing it with the transactions that she logged in her checkbook register. After calculating the transactions in the statement and he checkbook register, she realized that the statement showed more balance than her checkbook register. What could be the reason behind this discrepancy?

The bystander effect  for some reason my history teacher was talking about this 

Like many students at university, you may be unhappy about the results you attain in exams. you may feel that even with all you are doing there must be something more -- or different-- you could be doing to get better grades. we have all at some time or other heard of that student who only studies a couple of hours for final exams and scores a's every time. we stand in awe of those who seem to breeze through without undue effort and seem to need very little in the way of studying to nail an exam. the reasons for success, in what i think are the vast majority of cases, are less esoteric than many students think: successful students consistently apply a series of productive strategies with view to attaining clearly identified learning and grade goals throughout the academic term.