Second, reliability analysis was performed including discrimination (corrected item-total correlation), difficulty (mean) for each item and internal consistency (Cronbach's α) for the whole scale.
Specific values for the life skills-scales, and for intentions, attitudes and perceived risks at baseline along with representative items and used response scales are shown in table 2. If item-total correlation, difficulty or Cronbach's alpha exceed limiting values, scales are modified for data analysis by excluding items in order to increase psychometric quality.
The correlation of difficulties across the two occasions is good (mean = .704; range = .604 to.755) suggesting that item difficulties are stable across time.
The frequent and often abrupt climatic changes that occurred during the transition from the last cold stage to the present interglacial (the 'Late-glacial period') pose particular problems for stratigraphy and correlation, while difficulties are also encountered in developing a coherent independent dating framework for this important time interval.
There was a significant correlation between difficulty and post-intervention decisions [ 16 ]: as the difficulty score increased, the number of decisions to order an x-ray (which were mostly inappropriate) increased.
Content validity, item reliability (test retest, item-total correlation, item difficulty) and test reliability (internal consistency) were established.
Discrimination (corrected item-total correlation) and difficulty (mean) were again computed for each item.
The correlation between difficulty and effectiveness was analyzed by Spearman rank correlation; p values <0.05 were considered significant.
Inter and intra-rater reliability, internal consistency, item discrimination index, item total correlation, and difficulty were analyzed.
The reduced item pool was subjected to item analysis including the calculation of discrimination (corrected item-total correlation) and difficulty (mean) for each item.
