Passage
Lucid dreaming occurs when a person becomes consciously aware of a dream and uses executive decision-making skills to critically analyze the dream environment. Lucid dreamers are thus able to control certain aspects of their dreams, an ability that may occur intentionally, through practice, or unintentionally, usually after having noticed something bizarre or unrealistic in the dream. A lucid dreamer might choose to experience the sensation of flying, explore a custom-designed landscape, carry out a predetermined task, or practice a skill. Estimates suggest that about half the population has had a lucid dream, and about 10%-20% of people are considered frequent lucid dreamers experiencing such dreams regularly (at least once a month) .In one study, researchers asked participants to perform a difficult visuomotor task that involved throwing an object through a small moving target. Participants were organized into three groups, one group of frequent lucid dreamers and two groups of nonlucid dreamers. All three groups attempted the visuomotor task at midday in the research lab, before (pretest) and after (posttest) a single night's sleep at home. Lucid dreamers were asked to only practice the visuomotor task overnight during their lucid dream ("lucid practice" group) . One group of nonlucid dreamers practiced the task in the lab, right after the pretest ("waking practice" group) , and another group of nonlucid dreamers performed the pretest and posttest without practicing between the tests ("no practice" group) . The average improvement of hits (the number of times each participant successfully threw the object through the target) from pretest to posttest for each group is shown in Figure 1.
Figure 1 Median improvement in total hits for each group (Note: The notches represent the 95% confidence interval for the median.) The researchers proposed that a follow-up study be devised and conducted to control for any potential variability in each participant's sleep at home. The researchers suggested using the same study procedure except participants would sleep overnight for five consecutive nights in a sleep lab, where the timing and duration of sleep would be standardized. In order to eliminate any potential "first-night effects" (an initial reduction in sleep quality when sleeping in an unfamiliar environment) , researchers proposed that pretest and posttest measures each be taken before and after the third, fourth, and fifth night's sleep.
-Which of the following conclusions is most supported by Figure 1?

Question

Passage
Lucid dreaming occurs when a person becomes consciously aware of a dream and uses executive decision-making skills to critically analyze the dream environment. Lucid dreamers are thus able to control certain aspects of their dreams, an ability that may occur intentionally, through practice, or unintentionally, usually after having noticed something bizarre or unrealistic in the dream. A lucid dreamer might choose to experience the sensation of flying, explore a custom-designed landscape, carry out a predetermined task, or practice a skill. Estimates suggest that about half the population has had a lucid dream, and about 10%-20% of people are considered frequent lucid dreamers experiencing such dreams regularly (at least once a month) .In one study, researchers asked participants to perform a difficult visuomotor task that involved throwing an object through a small moving target. Participants were organized into three groups, one group of frequent lucid dreamers and two groups of nonlucid dreamers. All three groups attempted the visuomotor task at midday in the research lab, before (pretest) and after (posttest) a single night's sleep at home. Lucid dreamers were asked to only practice the visuomotor task overnight during their lucid dream ("lucid practice" group) . One group of nonlucid dreamers practiced the task in the lab, right after the pretest ("waking practice" group) , and another group of nonlucid dreamers performed the pretest and posttest without practicing between the tests ("no practice" group) . The average improvement of hits (the number of times each participant successfully threw the object through the target) from pretest to posttest for each group is shown in Figure 1.

Figure 1 Median improvement in total hits for each group (Note: The notches represent the 95% confidence interval for the median.) The researchers proposed that a follow-up study be devised and conducted to control for any potential variability in each participant's sleep at home. The researchers suggested using the same study procedure except participants would sleep overnight for five consecutive nights in a sleep lab, where the timing and duration of sleep would be standardized. In order to eliminate any potential "first-night effects" (an initial reduction in sleep quality when sleeping in an unfamiliar environment) , researchers proposed that pretest and posttest measures each be taken before and after the third, fourth, and fifth night's sleep.
-Which of the following conclusions is most supported by Figure 1?

Quizplus · Accepted Answer

11ecba2d_0c4e_fad6_a3bf_dd0b1fff98b1_MD0008_00 The results of the lucid dreaming study described in the passage are illustrated with a box-and-whisker plot, which is used to visually represent the median and the distribution of the data into quartile ranges: The upper quartile (Q3; 75% of the data lies below this value), shown as the top edge of the box. The median (50% of the data lies below this value), which is the line inside the box. The lower quartile (Q1; 25% of the data lies below this value), shown as the bottom edge of the box. The maximum and minimum data points, shown as whiskers, are data values no more than 1.5 times the interquartile range (IQR) from the edge of the box. The IQR is equal to the difference between the upper and lower quartiles. Outliers, shown as data points outside the maximum and minimum data points. Confidence intervals (CIs) represent a measure of uncertainty in a reported value by indicating how far the value reported might be from the true value (eg, true median). Theoretically, a 95% CI indicates that if the same population were sampled countless times and CIs were calculated each time, the resulting intervals would contain the true population value in approximately 95% of the cases. A notch that represents the 95% CI of the median is used on the box-and-whisker plot to estimate visually whether the medians of two groups are significantly different. If the notches across two groups do not overlap, the medians of the two groups are probably significantly different. In Figure 1, the notches of both the "waking practice" and "lucid practice" groups are higher than and do not overlap with the notch of the "no practice" group, so the two practice groups are assumed to have improved significantly more on the task than the "no practice" group. However, one cannot conclude from the figure that a significant difference exists between groups when notches do overlap. (Choice A) An individual from the "waking practice" group (not the "lucid practice" group) demonstrated the lowest improvement of all members. (Choice C) The "lucid practice" group's lowest quartile was completely below the "no practice" group's highest quartile, indicating less improvement for the "lucid practice" group's lowest quartile. (Choice D) Box-and-whisker plots provide information about the median, not the mean or the mode. Educational objective: Box-and-whisker plots visually represent the median value and interquartile range. Notched box plots show the 95% confidence interval around the median. If notches do not overlap, medians can generally be inferred to be statistically significantly different.

Passage Lucid Dreaming Occurs When a Person Becomes Consciously Aware of of a Dream