Find the Modal Class.

The provided frequency distribution table is incomplete. To accurately calculate the mean, median class, and standard deviation for all 50 patients, the full table with all class limits and their corresponding frequencies is required.

Based on the visible data:

Step 1: Find the Modal Class.
The modal class is the class interval with the highest frequency.
From the visible part of the table, the highest frequency is 18, which corresponds to the class interval 80-84.
The modal class is $\boxed{\text{80-84}}$.

Please provide the complete frequency distribution table so I can calculate the mean, median class, and standard deviation.