Preschoolers use both direct observation of statistical data and informant testimony to learn causal relationships. Can children integrate information from these sources, especially when source reliability is uncertain? We investigate how children handle a conflict between what they hear and what they see. In Experiment 1, 4-year-olds were introduced to a machine and 2 blocks by a knowledgeable informant who claimed to know which block was better at activating the machine, or by a naïve informant who guessed. Children then observed probabilistic evidence contradicting the informant and were asked to identify the block that worked better. Next, the informant claimed to know which of 2 novel blocks was a better activator, and children chose 1 block to try themselves. After observing conflicting data, children were more likely to say the informant's block was better when the informant was knowledgeable than when she was naïve. Children also used the statistical data to evaluate the informant's reliability and were less likely to try the novel block she endorsed than children in a baseline group who did not observe data. In Experiment 2, children saw conflicting deterministic data; the majority chose the block that consistently activated the machine as better than the endorsed block. Children's causal inferences varied with the confidence of the informant and strength of the statistical data, and informed their future trust in the informant. Children consider the strength of both social and physical causal cues even when they disagree and integrate information from these sources in a rational way.