Answer:
See Explanation
Step-by-step explanation:
The question is incomplete as the diameters of the Willapa Bay urchins were not given.
However, I'll give a general way to solve this problem.
Average is calculated using:
![Average = (\sum x)/(n)](https://img.qammunity.org/2022/formulas/geography/high-school/gdzqubzwusc1prey5m84i8d4hpfnkjwsxz.png)
i.e. Sum of all diameters divided by the number of bay urchins.
The diameter of urchins is usually between 6cm to 12cm; So, I will assume the following diameters for 10 urchins.
10cm, 8cm, 10cm, 7cm, 9cm, 10cm, 6cm, 10cm,8cm, 8cm
Using the above data, the average is:
![Average= (10+8+10+7+9+10+6+10+8+8)/(10)](https://img.qammunity.org/2022/formulas/biology/college/6ofvw38fuqxhsao7lvetqu0qmqsmyotxzw.png)
![Average= (86)/(10)](https://img.qammunity.org/2022/formulas/biology/college/a6vj9ary1nmv2ma08csrzht5j4hzatgm4d.png)
![Average= 8.6](https://img.qammunity.org/2022/formulas/biology/college/k1vkjyy3m07g6b2nk63nxgd30j8rgnez2u.png)