Final answer:
About 68 percent of the observations fall between 18 and 22 in a bell-shaped distribution with a mean of 20 and a standard deviation of 2, according to the Empirical Rule.
Step-by-step explanation:
The question relates to the Empirical Rule, sometimes known as the 68-95-99.7 rule, which is used in statistics to describe how data in a bell-shaped distribution is spread in relation to the mean and standard deviation. According to this rule, approximately 68 percent of the observations lie within one standard deviation of the mean in a normal distribution. For the data provided with a mean (average) of 20 and a standard deviation of 2, the range from 18 to 22 represents one standard deviation below and above the mean, respectively.
To estimate the percentage of observations that fall between 18 and 22, which is within one standard deviation from the mean, we simply refer to the Empirical Rule. This rule states that approximately 68 percent of the observations in a bell-shaped distribution are expected to fall within this range.
Therefore, we can conclude that approximately 68 percent of the observations fall between 18 and 22 in this particular bell-shaped distribution.