The question is asking to calculate the standard deviation $s$ from a frequency distribution table with different interval classes. Here is the breakdown of the table provided:

Steps to calculate standard deviation (using frequency distribution):

1. Find the midpoint ( $x_i$ ) for each class:
   Midpoint $x_i$ of a class interval can be found by taking the average of the lower and upper bounds of the class. $x_i = \frac{\text{Lower Bound} + \text{Upper Bound}}{2}$

2. Multiply each midpoint $x_i$ by the frequency $f_i$ to calculate $f_i x_i$.

3. Calculate the mean $\bar{x}$: $\bar{x} = \frac{\sum (f_i x_i)}{\sum f_i}$

4. Find the squared deviations $(x_i - \bar{x})^2$, and multiply them by the frequencies $f_i$ to get $f_i (x_i - \bar{x})^2$.

5. Sum up all $f_i (x_i - \bar{x})^2$, and divide by $\sum f_i - 1$ to find the variance.

6. Standard deviation $s$: $s = \sqrt{\frac{\sum f_i (x_i - \bar{x})^2}{\sum f_i - 1}}$

Let me calculate this step by step for you.The calculated mean $\bar{x}$ is 56.1, and the standard deviation $s$ is approximately 19.73.

Would you like more details on the calculations or any specific step?

Here are 5 related questions to explore further:

1. How would the standard deviation change if the frequencies were doubled?
2. What is the significance of the standard deviation in this context?
3. How would the calculation differ for a population standard deviation versus a sample standard deviation?
4. How can you calculate the variance from the standard deviation?
5. What other measures of spread (besides standard deviation) are commonly used in statistics?

Tip: In frequency distribution tables, the midpoint is crucial for representing the entire class interval with a single value.