So what was the question that she's trying to answer? Well, at least the way it's written, it seems like she's trying to answer whether or not her antibiotic works, whether it's an effective antibiotic, whether it's capable of killing bacteria. And you might be tempted to say, okay, well look, it looks like it killed, it killed more than 90% of the bacteria, or it very likely killed more than 90% of the bacteria, given the sample size and the margin error and all of that, but even if it is indeed the case that 95% of all of the bacteria died, it doesn't necessarily mean that it was caused by the antibiotic. Maybe it was caused by the plastic in the Petri dish. Maybe the air in the Petri dish was too cold or went bad, or maybe it was handled in a weird way, or maybe that bacteria was just a bad culture and it somehow just spontaneously died on its own. She can't say with confidence that it was definitely the antibiotic. In order for her to make that statement, she would have to run a proper experiment.