Cronbach's Alpha

Question 1

What is Cronbach’s alpha?

Answer 1

a) a way of assessing reliability by comparing the amount of shared variance, or covariance, among the items making up an instrument to the amount of overall variance.
b) if the instrument is reliable, there should be a great deal of covariance among the items relative to the variance.

Question 1

What is internal consistency?

Answer 1

refers to how well a survey, questionnaire, or test actually measures what you want it to measure; reliability

Question 2

How do you interpret Cronbach’s alpha?

Answer 2

a) Cronbach’s Alpha takes values between 0 and 1.
b) Generally, a high value represents good internal consistency.
c) 0.5-1.0 = poor, questionable, acceptable, good, excellent
d) less than 0.5 is unacceptable
c) Alpha is also affected by the length of the test. If the test length is too short, the value of alpha is reduced

Question 3

Cronbach’s alpha equation

Answer 3

𝛼 = (𝑁𝐶̅) / (𝑉̅+ (𝑁−1)𝐶̅ )

> N is the number of items
𝐶̅ is the average covariance of between-item pairs
𝑉̅ is average the variance

Question 4

Identifying variances and covariances in table

Answer 4

a) variances = diagonal
b) covariances = non-diagonal elements

Question 5

On what question types can cronbach’s alpha be calculated for?

Answer 5

for questions with numerical outcomes, including continuous variables, binary variables and rating scale variables, most commonly for a set of questions using the same Likert scale