The T score is a type of standard score that is based upon the normal curve with a mean of 50 and a standard deviation of 10 for the norm group. Test developers have derived norm tables that allow us to convert a person’s raw score (points earned) to the T score equivalents that would have been obtained if that person had been in the norm group. T scores permit a more meaningful comparison with a norm group than raw scores. Tests for admission to graduate and undergraduate schools (e.g., the Graduate Record Exam) typically use this type of standardized score. The formula frequently used for T score calculation is:

Where: X = raw score to be converted
= mean of the group of raw scores
SD = standard deviation of the raw scores
Example: Convert a raw score of 80 to a T score, where   = 75 and SD = 5.

RESEARCH ARTICLE
Source: LoGalbo, A., Sawrie, S., Roth, D. L., Kuzniecky, R., Knowlton, R., Faught, E., & Martin, R. (2005). Verbal memory outcome in patients with normal preoperative verbal memory and left mesial temporal sclerosis. Epilepsy and Behavior, 6 (3), 337€“41.
Introduction
LoGalbo et al. (2005) conducted a study to examine the risk of verbal memory loss in patients with known structural abnormality (i.e., left mesial temporal sclerosis by MRI) and normal preoperative verbal memory performance who undergo left ATL [anterior temporal lobectomy] (LoGalbo et al., 2005, p. 337). The researchers found that the patients exhibiting normal presurgical verbal memory are at risk for verbal memory declines following ATL. These results suggest that functional integrity of the left mesial temporal lobe may play an important role in the verbal memory outcome in this patient group (LoGalbo et al., 2005, p. 337). However, the researchers do recognize the limitations of their study and note that the small sample size restricts the generalization of the study findings.
Relevant Study Results
Seventeen patients with left temporal epilepsy, MRI-based exclusive left MTS [mesial temporal sclerosis], and normal preoperative verbal memory were identified (LoGalbo et al., 2005, p. 337). MTS is a structural abnormality in the brain. The patients selected for the study were considered to have normal’ preoperative verbal memory, defined as having preoperative performance across the learning (Acquisition) and long delayed free recall (Retrieval) portions of the California Verbal Learning Test (CVLT) of at least a T score above 40 (> 16%ile). The CVLT Acquisition score is the total number of words recalled across the five learning trials. The CVLT Retrieval score is defined as total number of words freely recalled after a 20-min delay. Both of these variables have been extensively employed as markers of verbal memory outcome following ATL [anterior temporal lobectomy] in several studies (LoGalbo et al., 2005, p. 339). Clinical characteristics of these patients are summarized in Table 2, and average CVLT Acquisition and Retrieval T scores are presented in Table 3.
The average drop in CVLT Acquisition T scores was 6.9, representing a decline of 15% from baseline performance. The average drop in CVLT Retrieval T scores was 9.6, representing a decline on average of 20% from baseline score (LoGalbo et al., 2005, p. 340).

LoGalbo, A., Sawrie, S., Roth, D. L., Kuzniecky, R., Knowlton, R., Faught, E., & Mar  tin, R. (2005). Verbal memory outcome in patients with normal preoperative verbal memory and left mesial temporal sclerosis. Epilepsy and Behavior, 6 (3), p. 339. Copyright © 2005, with permission from Elsevier, Inc.
a    L, left injection memory score (max value = 15); R, right injection memory score (max value = 15).
b    California Verbal Learning Test (CVLT) scores are reported as T scores.
TABLE 3     Average CVLT Acquisition and Retrieval T Scores and SRB Change Scores

LoGalbo, A., Sawrie, S., Roth, D. L., Kuzniecky, R., Knowlton, R., Faught, E., & Martin, R. (2005). Verbal memory outcome in patients with normal preoperative verbal memory and left mesial temporal sclerosis. Epilepsy and Behavior, 6 (3), p. 340.
STUDY QUESTIONS
1.    Which patients scored the lowest on the preoperative CVLT Acquisition? What was their T score?
2.    Which patient scored the highest on postoperative CVLT Retrieval? What was this patient’s T score?
3.    Did the patient in Question 2 have a decline in memory retrieval performance from before and after surgery? Provide a rationale for your answer.
4.    If a patient scored < 16%ile on the CVLT, what would his/her T score be less than?
5.    What is the mean ( ) and standard deviation (SD) for preoperative T score for CVLT Retrieval?
6.    Is the postoperative Acquisition T score for Patient 14 above or below the mean for the norm group? Provide a rationale for your answer.
7.    Discuss the change in CVLT Acquisition T scores for Patient 14 from before and after surgery. How do her T scores compare with the mean CVLT Acquisition T scores before and after surgery? What do these results indicate about this patient’s memory?
8.    Assuming that the distribution of scores for the postoperative Acquisition is normal, the middle 68% of the patients had T scores between what two values?
9.    If a patient had a raw score = 50, what would his/her preoperative CVLT Acquisition T score be?

Name:____________________________________________ Class: ____________________
Date: _________________________________________________________________________________
? EXERCISE 20     Questions to be Graded
1.    Which patient scored the highest on the preoperative CVLT Acquisition? What was his or her T score?
2.    Which patient scored the lowest on postoperative CVLT Retrieval? What was this patient’s T score?
3.    Did the patient in Question 2 have more of a memory performance decline than average on the CVLT Retrieval? Provide a rationale for your answer.
4.    What is the mean ( ) and standard deviation (SD) for preoperative T score for CVLT Acquisition?
5.    Is the preoperative Retrieval T score for Patient 5 above or below the mean for the norm of the group? Provide a rationale for your answer.
6.    Assuming that the distribution of the preoperative CVLT Retrieval T scores is normal, the middle 68% of the patients had T scores between what two values?
7.    Assuming that the distribution of scores for the postoperative CVLT Retrieval T scores is normal, the middle 68% of the patients had T scores between what two values?
8.    The researchers state that it appears that the functional integrity of the left temporal lobe, despite evidence of structural abnormality, plays a considerable role when it comes to memory outcomes following left ATL. Can the findings from this study be generalized to a larger population? Provide a rationale for your answer.
9.    If a patient had a raw score = 30, what would his/her postoperative CVLT Retrieval T score be?
10.    Did patients demonstrate more postoperative memory declines among CVLT Retrieval T scores than CVLT Acquisition T scores? Provide a rationale for your answer.
(Grove 145)
Grove, Susan K. Statistics for Health Care Research: A Practical Workbook. W.B. Saunders Company, 022007. VitalBook file.