Question

What can you do to avoid difficulties with reliability and validity?

Answer 1

Random errors are considered part of the reliability of a measurement.

Random errors are not attributable to a specific cause. If sufficiently large numbers of observations are made, random errors average to zero, because some readings over-estimate and some under-estimate.

You can control random errors including more number of observations.

Systematic errors are considered part of the validity of a measurement.

Systematic errors tend to fall in a particular direction and are likely due to a specific cause. Because systematic errors fall in one direction (e.g., I always exaggerate my athletic abilities) they bias a measurement.

By including randomness in the sampling or observations you can reduce this error.