A min heap is a binary tree where the value of each node is less than or equal to the values of its children. Given an array representation of a binary tree, write a function `check_min_heap(arr)` to determine if the array represents a min heap.
The array representation of a binary tree follows these rules:
- The root node is at index 0.
- For a node at index `i`, its left child is at index `2*i + 1` and its right child is at index `2*i + 2`.
#### Example Usage
```python [main.nopy]
print(check_min_heap([1, 2, 3, 4, 5, 6])) # Output: True
print(check_min_heap([2, 3, 4, 5, 10, 15])) # Output: True
print(check_min_heap([2, 10, 4, 5, 3, 15])) # Output: False
```
#### Constraints
- The input array will have at least one element.
- The elements of the array are integers.