inter-item correlations

Inter-item correlations look at the extent to which items are related to each other and/or to the total score. Inter-item correlations indicate how well the items are measuring the same content or construct. High correlations indicate the items are measuring a single understandable construct. Low correlations may indicate the item is not measuring the construct effectively. 

Inter-item correlations are an indicator of internal consistency reliability and may be used in addition or as an alternative to Cronbach alpha when a scale has a small number of items (e.g., <10). Because Cronbach's alpha is calculated based on the number of items in a scale, fewer items tend to result in lower alpha values, even if the items are well-correlated and therefore may not accurately reflect the scale's reliability. 

Measurement: Pearson’s r

Interpretation:  The ideal range of the mean inter-item correlation is 0.15 to 0.50. This suggests that the items are reasonably homogeneous but also possess unique variance. Lower than this and the items may not represent the concept of interest very well, higher than this and there may be elements of repetition.