Passage
Korsakoff syndrome (KS) is caused by a thiamin (vitamin B₁) deficiency that often results from chronic alcohol consumption. If KS is diagnosed during its earliest stages, its course may be reversed with thiamin supplements; otherwise, it progresses into a permanent type of dementia that includes severe cognitive dysfunction and memory loss. Alzheimer disease (AD) is associated with a different type of dementia that worsens over time, eventually causing memory loss, cognitive dysfunction, and severe brain atrophy.In one study, KS and AD subjects were assessed using the Corsi block-tapping task, which measures nonverbal memory. The experiment consisted of 10 KS subjects, 10 AD subjects, and 10 healthy control subjects. The control group was matched by age, gender, and premorbid IQ (intelligence quotient preceding the occurrence of symptoms) to the KS and AD groups.
Figure 1 Corsi block-tapping taskThe Corsi block-tapping task consists of nine wooden blocks placed randomly on a board (Figure 1) . To assess subjects' nonverbal memory, the experimenter touched four numbered blocks (numbers were visible only to the experimenter) in a specific pattern. Each subject was then asked to touch the same four blocks in the same sequence, either immediately or after a delay of 5-25 seconds. Subjects were required to perform a distractor task during the delay period. For the distractor task, subjects were asked to watch and reproduce a finger-tapping sequence first demonstrated by the experimenter. Experimenters would touch a finger on their right hand to a finger on their left hand according to a specific sequence (eg, index finger to ring finger, then pinky finger to middle finger) and the subjects would try to do the same.Results indicated that compared to controls, subjects with AD and KS were significantly impaired on the delayed memory task, although all subjects showed a significantly greater number of errors with increases in the delay interval.
-Based on study results and the legend below, which of the following graphs best displays the mean and 95% confidence intervals for accuracy scores for each group?

Question

Passage
Korsakoff syndrome (KS) is caused by a thiamin (vitamin B₁) deficiency that often results from chronic alcohol consumption. If KS is diagnosed during its earliest stages, its course may be reversed with thiamin supplements; otherwise, it progresses into a permanent type of dementia that includes severe cognitive dysfunction and memory loss. Alzheimer disease (AD) is associated with a different type of dementia that worsens over time, eventually causing memory loss, cognitive dysfunction, and severe brain atrophy.In one study, KS and AD subjects were assessed using the Corsi block-tapping task, which measures nonverbal memory. The experiment consisted of 10 KS subjects, 10 AD subjects, and 10 healthy control subjects. The control group was matched by age, gender, and premorbid IQ (intelligence quotient preceding the occurrence of symptoms) to the KS and AD groups.

Passage Korsakoff syndrome (KS) is caused by a thiamin (vitamin B<sub>1</sub>) deficiency that often results from chronic alcohol consumption. If KS is diagnosed during its earliest stages, its course may be reversed with thiamin supplements; otherwise, it progresses into a permanent type of dementia that includes severe cognitive dysfunction and memory loss. Alzheimer disease (AD) is associated with a different type of dementia that worsens over time, eventually causing memory loss, cognitive dysfunction, and severe brain atrophy.In one study, KS and AD subjects were assessed using the Corsi block-tapping task, which measures nonverbal memory. The experiment consisted of 10 KS subjects, 10 AD subjects, and 10 healthy control subjects. The control group was matched by age, gender, and premorbid IQ (intelligence quotient preceding the occurrence of symptoms) to the KS and AD groups. <strong>Figure 1</strong> Corsi block-tapping taskThe Corsi block-tapping task consists of nine wooden blocks placed randomly on a board (Figure 1) . To assess subjects' nonverbal memory, the experimenter touched four numbered blocks (numbers were visible only to the experimenter) in a specific pattern. Each subject was then asked to touch the same four blocks in the same sequence, either immediately or after a delay of 5-25 seconds. Subjects were required to perform a distractor task during the delay period. For the distractor task, subjects were asked to watch and reproduce a finger-tapping sequence first demonstrated by the experimenter. Experimenters would touch a finger on their right hand to a finger on their left hand according to a specific sequence (eg, index finger to ring finger, then pinky finger to middle finger) and the subjects would try to do the same.Results indicated that compared to controls, subjects with AD and KS were significantly impaired on the delayed memory task, although all subjects showed a significantly greater number of errors with increases in the delay interval. -Based on study results and the legend below, which of the following graphs best displays the mean and 95% confidence intervals for accuracy scores for each group? A) B) C) D)

Figure 1 Corsi block-tapping taskThe Corsi block-tapping task consists of nine wooden blocks placed randomly on a board (Figure 1) . To assess subjects' nonverbal memory, the experimenter touched four numbered blocks (numbers were visible only to the experimenter) in a specific pattern. Each subject was then asked to touch the same four blocks in the same sequence, either immediately or after a delay of 5-25 seconds. Subjects were required to perform a distractor task during the delay period. For the distractor task, subjects were asked to watch and reproduce a finger-tapping sequence first demonstrated by the experimenter. Experimenters would touch a finger on their right hand to a finger on their left hand according to a specific sequence (eg, index finger to ring finger, then pinky finger to middle finger) and the subjects would try to do the same.Results indicated that compared to controls, subjects with AD and KS were significantly impaired on the delayed memory task, although all subjects showed a significantly greater number of errors with increases in the delay interval.
-Based on study results and the legend below, which of the following graphs best displays the mean and 95% confidence intervals for accuracy scores for each group?

Quizplus · Accepted Answer

Error bars may represent several types of statistics (eg, confidence intervals, standard deviations, standard errors). Interpretation of error bars depends on which statistic is depicted. Confidence intervals (CIs) address how well a sample statistic (eg, mean) estimates a true population value by providing a range of values that is likely to contain the population parameter (eg, mean) of interest. On the graph, the points depict the group mean and the CIs depict the uncertainty of the mean considering the sample size and the variability of the measurement. Graphically, CIs may help determine statistical significance: Whenever CIs do not overlap, group means are statistically significantly different. However, the opposite is not always true; whenever CIs overlap, group means may or may not be statistically different. This study used a mixed factorial design. It assessed between-groups factors by testing two or more groups simultaneously to examine differences between groups. It also evaluated within-groups (or repeated measures) factors by assessing the same subjects at several time points to determine if there was a significant change over time. This study produced two statistically significant findings: (1) the AD and the KS groups were significantly impaired on the delayed memory task compared to controls (between-groups finding), and (2) all subjects showed a significantly greater mean number of errors as the delay interval increased (within-groups finding). Therefore, an accurate representation of results should include the following: (1) CIs for the AD and the KS groups that do not overlap with those for the control group, and (2) CIs for the final time points (ie, 25-second delay interval) in all groups that do not overlap with their corresponding initial time points (ie, 0 seconds). (Choices A and B) The CIs for the KS and the AD groups do not overlap, suggesting that subjects with AD and KS performed significantly differently compared to each other, which was not a finding mentioned in the passage. (Choice D) Every CI for the control group at each delayed condition included the initial time point (ie, 0 seconds) mean score, suggesting that performance for controls remained unchanged. This representation contradicts the finding that all subjects showed a statistically significant greater mean number of errors as the delay interval increased. Educational objective: Between-groups factors compare two or more groups to determine whether there is a difference between group outcome means. Within-groups factors (repeated measures) compare the outcomes for the same group at different times to determine whether there is a change in the outcome. Confidence intervals (CIs) graphically convey the uncertainty of statistics (eg, mean); if CIs do not overlap, the two means are statistically significantly different; however, the opposite is not always true.

Passage Korsakoff Syndrome (KS) Is Caused by a Thiamin (Vitamin B1)

Passage Korsakoff Syndrome (KS) Is Caused by a Thiamin (Vitamin B₁)