go green rating scale | 5
Reliability and Validity
Reliability of measurement addresses how well an instru-
ment consistently measures what it purports to measure.
The validity of a scale determines how well the scale
measures what it purports to measure.
Indicators of reliability can be computed by examining
internal consistency, test-retest reliability, or inter-rater
consistency, depending on the purpose and design of the
scale or instrument.
Internal consistency reliability reflects the consistency
of measurement on different portions of the test or scale.
The higher a scale’s internal consistency reliability, the
more accurately one can predict performance on any
subset of guidelines or items based on the performance of
Although an important measure of any scale’s technical
merit, it was not anticipated that measures of internal
consistency would be that high (approaching 1.0)
for the Go Green Rating Scale because, by design, the
scales measure many different aspects of the child care
environment from air quality to recycling practices.
The accuracy of ratings on one scale may or may not
predict ratings on other scales. However, two measures
of internal consistency reliability—split-half reliability
and coefficient alpha—were calculated for the Go Green
Rating Scale using scores from the sixty-four guidelines.
Split-half reliability was computed between total scores
based on the thirty-two odd-numbered guidelines and
total scores based on the thirty-two even-numbered
guidelines. The resulting correlation was then converted
by the Spearman-Brown prophesy formula to an estimate
of the reliability coefficient for the full length of the Go
Green Rating Scale. The final split-half reliability coeffi-
cient was .73.
Coefficient alpha is another type of internal consistency
reliability. While split-half reliability is based on a par-
ticular way of dividing the items into halves (here it was
done by odd-numbered guidelines and even-numbered
guidelines), coefficient alpha is the average of the results
from all possible divisions. Coefficient alpha is a measure
of the uniformity or homogeneity of items/guidelines
throughout the scale. For the Go Green Rating Scale the
alpha was .81. As anticipated, both reliability values dem-
onstrate a moderate, but not high, degree of relationship
among the various aspects of a child care environment
as measured by the sixty-four guidelines of the Go Green
Consistency in measurement over time (test-retest reli-
ability) was not computed for the Go Green Rating Scale.
By design, the Go Green Rating Scale can also be an
intervention tool, that is, something that can be used to
improve the greenness of the child care environment and
a future rating. Therefore, change or improvement in