As cited in Golafshani, N. (2003):
Joppe (2000) defines reliability as:
â€¦The extent to which results are consistent over time and an accurate representation of the total population under study is referred to as reliability and if the results of a study can be reproduced under a similar methodology, then the research instrument is considered to be reliable. (p. 1)
Joppe (2000) provides the following explanation of what validity is in quantitative research:
Validity determines whether the research truly measures that which it was intended to measure or how truthful the research results are. In other words, does the research instrument allow you to hit “the bullâ€™s eye” of your research object? Researchers generally determine validity by asking a series of questions, and will often look for the answers in the research of others. (p. 1)
two other websites gathered via google search:
Reliability and Validity: What’s the Difference?
Colorado State University Writing Guide: Overview: Reliability and Validity