To determine the upper quartile from a cumulative frequency graph, you need to locate the 75th percentile on the vertical axis.

The upper quartile, also referred to as the third quartile (denoted as $Q_3$), is the value below which 75% of the data points lie. To find $Q_3$ on a cumulative frequency graph, follow these steps:

1. Identify the Total Frequency: Begin by identifying the total number of data points, which corresponds to the highest value on the cumulative frequency axis.

2. Calculate 75% of the Total Frequency: Compute 75% of the total frequency by multiplying the total frequency by $0.75$. For instance, if the total frequency is $100$, then $75\%$ of $100$ is $75$.

3. Locate the 75th Percentile on the Graph: On the vertical axis (the cumulative frequency axis), find the value you calculated in the previous step. Draw a horizontal line from this point until it intersects the cumulative frequency curve.

4. Read the Corresponding Value on the Horizontal Axis: From the intersection point, draw a vertical line down to the horizontal axis (which represents the data values). The point where this line intersects the horizontal axis represents the upper quartile.

By following these steps, you can accurately determine the upper quartile from a cumulative frequency graph, enhancing your understanding of the data distribution.