T-Scores


Using the SCAS T-Scores


The SCAS is intended as an indicator of the number and severity of anxiety symptoms. It is not designed to be a diagnostic instrument for use in isolation. Where a clinical diagnosis is required it should be used as an adjunct to clinical interview. It may also be used for identification of children “at risk” and for whom further assessment is recommended to determine need for intervention. Similarly, it provides an indicator of response to treatment. It has also been used in several studies to identify children for whom early intervention or prevention is warranted on the basis of elevated anxiety symptoms being a risk factor for the development of future mental health problems (Barrett & Turner, 2001) .


There are various ways in which cut-off points can be established. The following method uses T-Scores and takes into account the age and gender to the young person. It also considers that high anxiety status may be reflected in both the total score and an elevated subscale score. Children may report elevated scores on the SCAS in two ways: in terms of elevated total scores and high scores on one or more subscale scores. Although the majority of children who report a high total score also report a high score on one or more subscales, this is not always the case. Thus, for clinical assessments, we recommend examining the total and subscale scores. For screening purposes in community samples, it may be sufficient to use the total score for identification of children at risk.


What Are T-Scores?


T-Scores enable the comparison of a young person's scores against norms from an equivalent age and gender group. AT-score is a standardized score that is calculated from the total distribution of scores within the community sample. Scores are rescaled so thatT-scores have a mean of 50 and a standard deviation of 10. Scores within one standard deviation (ie. a T-score of 10) above the mean on any dimension are regarded as being within the normal range on that dimension.

This process ensures that all subscales and the total score can be interpreted along the same scale, with the same mean and standard deviation, even though they initially had different numbers of items and different non-transformed means.


A T-score of 10 above the mean of 50 represents a value of 1 standard deviation above the mean and is indicative of elevated anxiety. As noted above the SCAS should not be used as a diagnostic instrument, in the absence of a clinical interview. We suggest using a T-score of 60 as indicative of sub-clinical or elevated levels of anxiety. This justifies further investigation and confirmation of diagnostic status using clinical interview.


The cut-off points used for T-scores depend on the purpose of the assessment and different authors suggest different cut-points that should be regarded as indicative of clinical or subclinical levels of psychopathology. A T-score of 70 or above reflects the top 2% of the population, whereas a T-score of 65 or above represents approximately the top 6%. Given that the SCAS is also used to screen children “at risk” for the emergence of anxiety disorders as a consequence of elevated anxiety symptoms (Dadds et al., 1999) , we have defined an “elevated” range of scores for T-scores above 60. A T-score of 60 or above reflects around the top 16% of the population.


Scoring Templates for Determining the T-Scores for SCAS


The attached scoring sheets can be downloaded and used to determine SCAS T-scores. It is important to use the correct sheet based on the child’s age and gender. The raw scores must first be calculated for each subscale and the total score. Then, the raw scores are circled on the sheet and the corresponding T-Score is identified from the T-score column. The raw score and corresponding T-score can be recorded at the bottom of the page.  Given the difference in means across age groups and gender, it is important to use the appropriate table.


YOU CAN DOWNLOAD THE SCAS T-SCORE TEMPLATES HERE

 
T scores for boys aged 8 - 11 years Download PDF
scores for boys aged 12 - 15 years Download PDF
scores for girls aged 8 - 11 years Download PDF
scores for girls aged 12 - 15 years Download PDF



How Were the T-Scores Computed?


The following section describes how the T-scores were calculated. The procedure for assigning T-Scores followed that outlined by Achenbach & Rescorla (2001) . This was performed separately for the total score and each subscale. For the SCAS this process was done separately for girls and boys and for younger/older children. First the cumulative frequency distribution of each score was determined, with each raw score then assigned to the midpoint of the percentile range that it spanned. T scores were then allocated to these mid-point percentile scores.


To take into account the positively skewed distributions and need for greater differentiation between high scores rather than low scores (for clinical use) we used to following procedure  :-

- we assigned T score of 40 to all raw scores also close as possible to the 15.7th percentile and below for each subscale. This point reflects 1 SD below the mean.

- To facilitate comparisons across subscales, T scores at the lower end were collapsed into T = 40 or below.

- A T-score of 50 was allocated to the score most closely approximating to the 50th midpoint percentile.

- At the high end of scores T scores the size of the sample a T-score of 70 was allocated to the score closest to the 98th midpoint percentile. T-scores above the 98th percentile (T score =70) are less accurate given the relatively low prevalence of such high scores in the community sample. Thus scores above the 98thpercentile were collapsed into T=70 and above.


- T scores were then allocated for 45, 55, 60, 65 and 70 based on midpoint percentiles:

T = 70: 98th %ile (50 + 34.13 + 13.59)

T = 65: 94th %ile

T = 60: 84th %ile (50 + 34.13)

T = 55: 70th %ile

T = 50: 50th %ile

T = 45: 29th %ile

T = 40: 16th %ile (50 - 34.13)

Note: 34.13 percent = 1SD above/below the mean.

34.13+13.59 = 2 SDs above/below mean

In keeping with Achenbach & Rescorla (2001) we emphasize that raw scores rather than T-scores should be used for statistical analyses, where the full range of scores is important.