The median is the value placed in the half position of the list. In this case, we have 13 values, then there are 6 values on the left and 6 values on the right of the median.
median = 36
To find the lower quartile (Q1) we only need to consider from the minimum to the median. And find the value in the half. In this case, there are 6 values, then we need to compute the average between the 3rd and 4th values, as follows:
lower quartile (Q1) = (29+29)/2
lower quartile (Q1) = 29
Similarly, the upper quartile is in the half of the values from the median to the maximum. In this case, we need to compute the average between the 11th and 12th values, as follows:
upper quartile (Q3) = (40 + 44)/2
upper quartile (Q3) = 42
The other values of the five-summary are:
minimum = 26
maximum = 55
The interquartile range (IQR) is computed as follows:
IQR = Q3 - Q1
IQR = 42 - 29
IQR = 13