A store is equipped with self-service automatic checkouts where the customer scans their own items. The checkout software regularly triggers verification requests.
The check can be either ``complete'': the store employee then scans all of the customer's items again; or ``partial'': the employee then selects one or more of the customer's items to verify that they have been scanned correctly.
If a check is triggered, it is a complete check one time out of ten. When a complete check is triggered, a customer error is detected in $30\%$ of cases. When a partial check is performed, in $85\%$ of cases, there is no error.
A check is triggered at an automatic checkout. We consider the following events:
- T: ``The check is a complete check'';
- E: ``An error is detected during the check''.
We denote $\bar{T}$ and $\bar{E}$ the complementary events of $T$ and $E$.
- Construct a probability tree representing the situation and then determine $P(\bar{T} \cap E)$.
- Calculate the probability that an error is detected during a check.
- Determine the probability that a complete check was performed, given that an error was detected. The answer will be given rounded to the nearest hundredth.