The normative calculator is a tool for converting the patient’s raw scores on the Clock Drawing Test (CDT), Shulman version to derived scores, i.e. percentiles, as a measure of how the patient performs compared to other people of the same age, gender and education level. The calculator covers the age range 25 – 95 years.
Instructions
Enter the patient’s age, gender, education level (in years), and attained CDT-score (0 – 5 points).
Gender
Education
Age
CDT score
Percentile:
The percentile is the proportion of the population at same age, sex and educational level that has equal or lower score on the CDT.
Evaluation of test results
As a rule of thumb, a score between the 16th and 84th percentiles is usually considered within the normal/average range; a score between the 2nd and 15th percentile indicates below the average range; and a score below the 2nd percentile implies significantly below the average range («pathological range»). However, precaution in the interpretation of test scores is always required. Evaluation of a patient’s test scores should be done on an individual basis, and, among others, take into consideration the patient’s estimated premorbid cognitive functioning level and motivation in the test situation.
The normative estimates are based on a regression model developed in a sample of individuals aged 25-89 years with 2-30 years of education.
Results for age and education combinations that were rare or absent in the normative sample should be interpreted with caution. This may be particularly relevant for indiviudals with the lowest or highest levels of education.