The upper quartile is the value of the middle of the second set, where 75% of the values are smaller than Q3 and 25% are larger.

The upper quartile, also known as the third quartile (Q3), is a statistical measure used to divide a dataset into four equal parts. It is the value below which 75% of the data falls.


To understand why option 'C' is the correct answer, let's break down the quartiles and their corresponding percentages.

- First Quartile (Q1): The first quartile is the value below which 25% of the data falls. It represents the lower boundary of the second quarter of the data. In other words, 25% of the data points are smaller than or equal to Q1.

- Second Quartile (Q2) or Median: The second quartile is the value that separates the data into two equal halves. It represents the middle value of the dataset. 50% of the data points are smaller than or equal to Q2, and 50% are larger.

- Third Quartile (Q3) or Upper Quartile: The third quartile is the value below which 75% of the data falls. It represents the upper boundary of the third quarter of the data. In other words, 75% of the data points are smaller than or equal to Q3.


Now, let's relate this information to the answer options provided:

a) Lowest 25%: This option refers to the first quartile (Q1), not the upper quartile (Q3). Therefore, it is not the correct answer.

b) Lowest 50%: This option refers to the second quartile (Q2) or the median, not the upper quartile (Q3). Therefore, it is not the correct answer.



d) Top 75%: This option refers to the entire dataset, not just the upper quartile (Q3). Therefore, it is not the correct answer.


The upper quartile (Q3) represents the value below which 75% of the data falls. Therefore, option 'C' correctly identifies the upper quartile as the lowest value of the top 25% of the dataset.