Measurement is an important part of the scientific process. The
key aspects concerning the quality of scientific measures are
reliability and validity. Reliability is a measure of the
internal consistency and stability of a measuring device.
Validity gives us an indication of whether the measuring device
measures what it claims to. Internal consistency is the degree
in which the items or questions on the measure consistently
assess the same construct. Each question should be aimed at
measuring the same thing. Internal consistency is often measured
using Cronbach’s Alpha — a super-correlation of all the items on
the scale. If the score is .70 or higher the measurement is
acceptable. However, .80 or higher is preferable. It is also
important to consider the context when considering the score
that reflects internal consistency. Stability is often measured
by test / retest reliability. The same person takes the same
test twice and the scores from each test are compared. A high
correlation between the two test sco