Answer: It is shown that the conditions of the expert's experiment were substantially similar to the conditions of the store's floor when the plaintiff slipped.
Explanation:
The condition under which the court should admit the testimony is that it is shown that the conditions of the expert's experiment were substantially similar to the conditions of the store's floor when the plaintiff slipped.
The testimony of the expert will only be relevant and applicable of it was similar to the scenario which led to the accident. In such case, it will be admissible if it's relevant.
As long as the conditions of the experiment of the expert replicated the conditions regarding the accident, then the experiment is said to be relevant.