In the data set below, what is the upper quartile? \( \begin{array}{llllll}4 & 5 & 7 & 9 & 9 & 9\end{array} \)

To find the upper quartile, also known as the third quartile (Q3), you first need to arrange your data set in ascending order, which it already is: \(4, 5, 7, 9, 9, 9\). The upper quartile is the median of the upper half of the data set. Since there are six values, the upper half consists of the last three values: \(9, 9, 9\). The median of these three values is \(9\). Therefore, the upper quartile is \(9\). A fun way to remember this is that the upper quartile is where three-quarters of the data lies below, so you can imagine it as the “VIP lounge” of your data set where the top scores hang out!