What are the (a) measurement errors and (b) recording mistakes?

(a) Measurement errors : As a very simple example, suppose each student in a class is asked to measure the length of the teacher’s table in the class room. Every student is provided a separate measuring tape. After comparing the measurement taken by the students, we will surely find that the measurements are not identical. The differences in measurements may arise because some students measured upto the nearest of the unit, while others measured to be nearest of the tenth place of decimal. Rounding of errors will always be there. Difference in measurements may also occur due to differences in measuring tapes themselves, due to manufacturing defects. Some students may also be careless. These are called measurement errors.

(6) Recording mistakes : The enumerator or the respondent may commit errors in recording data; for example, he may record 13 instead of 3, and so on. Sometimes the handwriting is so bad and unclear that the tabulator may misread the recorded answers, while transferreing data to files or computer.