Symbol Digit Modalities Test - Communicate-ed

How to calculate standard scores for the

Symbol Digit Modalities Test

SDMT was first published in 1973 Author: Aaron Smith Published by:

Western Psychological Services California USA

PO Box 2652, Maidenhead SL6 8ZL T: 0845 3311 492 F: 0871 918 2330

E: admin@communicate-.uk W: municate-.uk

Background Information

The SDMT manual does not provide Standard Scores, so for assessments in the UK, where Standard Scores are the most common method for reporting information from educational assessments, a standard score must be calculated.

WPS, copyright holders and publishers of the SDMT () recommend that practitioners use a formula recognised by statisticians in their field. The formula used in this document is a standard formula widely used by educational statisticians. Practitioners working in other fields should check the validity of the formula for their own area of work. We have contacted WPS to inform them of this adaptation of the scoring. The standardised scores in this document are calculated using means and standard deviations taken from pages 5 and 6 of the SDMT manual. Because of the limited sample size upon which these historic figures were based, a very few of the standardised scores look anomalous compared with their neighbouring scores. Assessors using SDMT in assessments for the Disabled Student's Allowance should refer to the document 'Updated Guidance on the use of the Symbol Digit Modalities Test' produced by STEC (the SpLD Test Evalation Committee) for further guidance.

Calculating Standard Scores for the SDMT

Using the tables on pages 5 and 6 of the manual, please refer to the mean and the standard deviation (in brackets) for the appropriate age group Subtract the mean score from the student's raw score Divide this answer by the standard deviation Multiply this answer by 15 Add 100 to this answer Round up or down for the standard score

For example: A student aged 26, with more than 12 years of education, completing the written SDMT, acheving a Raw Score of 51 1) Subtract the mean score from the student's raw score 51 - 57.72 = -6.72 2) Divide this answer by the standard deviation -6.72 ? 9.08 = -0.74 3) Multiply this answer by 15 -0.74 x 15 = -11.10 4) Add 100 to this answer -11.10 + 100 = 88.9 5) Round up or down for the standard score 89

With thanks to Stephanie Greenslade (Cambridge undergraduate) and Anne Pinot de Moira, Fellow of the Royal Statistical Society, Cstat. for their invaluable input to this project.

Boys Written SDMT

Age

8

9

10

11

12

13

14

15

16

17

Raw Score

5

61 60 ................
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