Question

In an intelligence test, the average score is 100, with scores spread out on each side between 70 and 130. If we were to fold over this curve, it would be symmetrical, wherein the left and right sides are mirror images of each other. The shape of this curve is known as ____.

1) an average distribution.
2) a normal distribution.
3) a bilateral distribution.
4) a clustered distribution.

Answer 1

2) a normal distribution

The symmetrical curve where intelligence test scores are spread out evenly on each side of the average score is known as a normal distribution. A score of 115 is one standard deviation above the mean, while a score of 70 is two standard deviations below the mean.

Step-by-step explanation:

In an intelligence test, the average score is typically set to 100, with scores dispersed symmetrically on either side. This symmetric, bell-shaped curve indicates that the distribution of scores is normal distribution. The term normal distribution accurately describes this kind of symmetrical spread around the mean in a dataset. It is characterized by its bell-shaped curve whereby most of the data is clustered around the mean, with frequencies decreasing as you move away from the center. In the context of intelligence tests, a score that is one standard deviation above or below this mean is within the average range, and a majority of people's scores fall within this region.

Regarding a score of 115, it would be described as "one standard deviation above the mean," while a score of 70 is "two standard deviations below the mean." Given that the scores follow a normal distribution, any score that is within one standard deviation above or below the mean (between 85 and 115) is considered average. Consequently, around 68% of the population has IQ scores in this range.