Each of the following must be included in an insurable risk, except?

An insurable risk requires specific characteristics to be effective and functional within the realm of insurance. One of the essential elements is that the risk must involve a large group of similar risks. By grouping similar risks, insurance companies can more accurately predict loss occurrences and set appropriate premiums.

Having a "large group with dissimilar members" does not fit the traditional model of insurable risks, which typically focus on large homogeneous groups where characteristics are similar, allowing for more predictable risk assessment. Insuring a diverse array of risks may complicate pricing and create challenges in assessing the likelihood of loss.

In contrast, elements like a calculable chance of loss and accidental losses are fundamental aspects of insurable risks, as they ensure that the risks can be quantified and managed appropriately. Similarly, excluding catastrophic perils can help insurers mitigate their exposure to events that would lead to significant financial loss, thus maintaining stability within their risk management operations.