Cronbach alpha

Cronbach alpha explores how well the individual items of a measure are measuring the same construct. The value of alpha is obtained by exploring the inter-relatedness of the items within a measure (how well the items correlate with each other). The reliability of a measure is closely associated with its validity (how well a measure, measures what it purports to measure). A measure cannot be valid unless it is reliable.  Because alpha is a property of the scores on a measure from a specific sample, alpha should be calculated each time the test is administered

 

Interpretation:

Values range from 0 to 1

• Values of .70 and above are usually considered acceptable

• Values between .80 and .90 are considered good

• Values above .90 are considered excellent, indicating very high reliability

• Values below .70 may indicate a problem with reliability e.g., some items may not be measuring the same construct