To calculate the interquartile range (IQR), we follow these steps:

1. Arrange the data in ascending order:

   15, 29, 30, 35, 36, 36, 37, 37, 38, 40, 41, 42, 43, 43, 44, 46, 50, 52, 53, 55

2. Find Q1 (the first quartile): Q1 is the median of the lower half of the data (excluding the overall median). The lower half of the data is:

   15, 29, 30, 35, 36, 36, 37, 37, 38, 40

   The median of this set is 36.5.

3. Find Q3 (the third quartile): Q3 is the median of the upper half of the data (excluding the overall median). The upper half of the data is:

   41, 42, 43, 43, 44, 46, 50, 52, 53, 55

   The median of this set is 46.5.

4. Calculate the IQR:

   $\text{IQR} = Q3 - Q1 = 46.5 - 36.5 = 10$

Thus, the interquartile range (IQR) is 10.

Would you like further explanation or details on any step?

Here are 5 related questions:

1. What does the interquartile range (IQR) tell us about data spread?
2. How do quartiles help in identifying outliers?
3. Can the IQR be used to identify the skewness of data?
4. What is the difference between range and IQR?
5. How does changing one number affect the IQR?

Tip: The IQR is particularly useful in identifying outliers, which are values that lie 1.5 times the IQR above Q3 or below Q1.