We are given a data set and we are asked to determine what could be the origin of the errors.
The errors in measurement are usually due to the resolution of the measuring device. This means that the device with which we are doing the measurement has a resolution that makes it impossible to differentiate between small quantities.
To improve this problem what can be done is to change the instrument of measurement for one with a higher resolution.
Another cause of errors is that the measurement is done by different persons. For example, if a person measures the distance from one point to another is possible that this measurement differs from the measurement done by another person. To improve this issue, all measurements should be done by the same person.
Another problem can be the calibration of the instrument since as the instrument is used for several measurements its ability to get correct measurements decreases. To avoid this error, instruments must be calibrated regularly.
Finally, another possible source of error is human errors that could be due to poor techniques or error transcribing the data. This can be improved by being extremely careful when making the measurements.