Passage
Psychophysiology examines the relationship between the properties of a physical stimulus (eg, amplitude of sound waves) and how we perceive that stimulus (eg, loudness) . However, this relationship is often accompanied by a degree of uncertainty as the stimulus of interest, or signal, can be confounded by various sources of noise. Noise can be either external (arising from the environment) or internal (arising from physiological sources) .To investigate the effect of distraction on auditory perception, researchers tested the ability of subjects to detect auditory tones presented during a visual-memory task. The study included 90 participants age 18-65, and each participant completed 10 trials. Trials consisted of five 800-Hz tones presented randomly while participants viewed a set of 15 sequential pictures of common objects on a computer screen. The objects fell into one of three categories: animals, vehicles, or things that make noise. Half the participants were asked to memorize as many objects as they could (objects group) , and half were asked to remember only the categories of objects they saw (categories group) . Tones were presented bilaterally within a range of 0-20 dB. Participants noted when they detected a tone during the trial by pressing a button. Results of the study are shown in Figure 1.
Figure 1 Mean percentage of tones correctly identified in each visual-memory task group (Note: Error bars indicate 95% confidence intervals.)
W. Yost ©2007 Academic Press.
-Which of the following conclusions can be drawn from the study as it is described in the passage?

Question

Passage
Psychophysiology examines the relationship between the properties of a physical stimulus (eg, amplitude of sound waves) and how we perceive that stimulus (eg, loudness) . However, this relationship is often accompanied by a degree of uncertainty as the stimulus of interest, or signal, can be confounded by various sources of noise. Noise can be either external (arising from the environment) or internal (arising from physiological sources) .To investigate the effect of distraction on auditory perception, researchers tested the ability of subjects to detect auditory tones presented during a visual-memory task. The study included 90 participants age 18-65, and each participant completed 10 trials. Trials consisted of five 800-Hz tones presented randomly while participants viewed a set of 15 sequential pictures of common objects on a computer screen. The objects fell into one of three categories: animals, vehicles, or things that make noise. Half the participants were asked to memorize as many objects as they could (objects group) , and half were asked to remember only the categories of objects they saw (categories group) . Tones were presented bilaterally within a range of 0-20 dB. Participants noted when they detected a tone during the trial by pressing a button. Results of the study are shown in Figure 1.

Figure 1 Mean percentage of tones correctly identified in each visual-memory task group (Note: Error bars indicate 95% confidence intervals.)
W. Yost ©2007 Academic Press.
-Which of the following conclusions can be drawn from the study as it is described in the passage?

Quizplus · Accepted Answer

11ecba2d_0c6f_2d27_a3bf_775d3e577c5a_MD0008_00 Error bars may represent several types of statistics, such as confidence intervals (CIs), standard deviations, or standard errors. The interpretation of the error bar depends on which statistic is depicted. CIs (shown in Figure 1) represent a measure of uncertainty in a reported value by indicating how far the value reported might be from the true value (eg, true mean). 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. As the sample size increases and the standard deviation decreases, the standard error of the mean decreases and the CI becomes narrower (ie, more precise). Although the mean percent detection calculated for the categories group was greater than that calculated for the objects group, the 95% confidence intervals for the two experimental groups are shown to overlap, implying that the difference may or may not be statistically significant. Nonoverlapping CIs always imply a statistically significant difference between groups. However, the opposite is not necessarily true (Choice D). (Choice A) Although participants did span a wide age range, the researchers did not report a relationship between age and tone detection. (Choice B) No conclusions can be drawn about the difficulty of the two memory tasks as this was not directly measured in the experiment. Educational objective: Overlapping confidence intervals indicate that the difference between groups may or may not be statistically significant.

Passage Psychophysiology Examines the Relationship Between the Properties of a Physical