A symmetrical, bell-shaped curve that describes the distribution of many types of data; most scores fall near the mean (about 68 percent fall within one standard deviation of it) and fewer and fewer near the extremes.

• A. Normal curve (normal distribution)
• B. Reliability
• C. Standardization
• D. Aptitude test

Answer: (A)

The normal distribution is the concept at play here—a symmetric, bell-shaped curve that many real-world data approximate. In this distribution, values cluster around the mean, and the spread is described by the standard deviation. A key fact is the 68-95-99.7 rule: about 68% of observations fall within one standard deviation of the mean, with fewer data as you move further away. This exactly matches the description provided: a bell-shaped, symmetric curve with most scores near the mean and about 68% within one standard deviation. The other terms refer to different ideas (reliability is about consistency, standardization is about creating comparable scales, and aptitude tests are a type of assessment), so they don’t describe this distribution.