Which type of frequency distribution shows the fraction or proportion of observations in categories?

The correct answer is the relative frequency distribution. This type of frequency distribution provides insights into how the observations are distributed across different categories by reporting the fraction or proportion of the total observations that lie within each category.

In a relative frequency distribution, the relative frequency for each category is calculated by dividing the number of observations in that category by the total number of observations. This allows for easier comparisons between categories, especially when sample sizes vary, since it standardizes the data into proportions or percentages of the total.

By contrast, other types of distributions serve different purposes. A percent frequency distribution expresses the same information as relative frequency but in percentage terms. Cumulative frequency distribution accumulates counts of observations, showing how many observations fall below a certain value, which is more useful for determining thresholds than for proportions. A standard frequency distribution presents the counts or frequencies without expressing them as fractions or proportions, which does not provide the same level of comparative insight as relative frequencies do.