Final answer:
In a box plot, 75% of the data falls below the third quartile, which corresponds to the 75th percentile of the data set.
Step-by-step explanation:
The question refers to the characteristics of a box plot. A box plot, also known as a box-and-whisker plot, visually displays the distribution of a data set and divides it into quartiles. The first quartile (Q1) corresponds to the 25th percentile, which means 25% of the data falls below this point. The second quartile, or the median, lies at the 50th percentile and divides the data into two equal halves. The third quartile (Q3) corresponds to the 75th percentile. This means that 75% of the data falls below the third quartile.
To answer the specific question: What percentage of the data in a boxplot is below the third quartile? The correct answer is 75%. This is based on the definition of the third quartile, marking the upper end of the interquartile range (IQR), which contains the middle 50% of the data.