Is one anomaly enough to disprove a hypothesis? If not, how many are? Why is it important that scientists use all of their results and not just some of them? What should we do if the evidence neither supports nor contradicts the hypothesis?

Is one anomaly enough to disprove a hypothesis? If not, how many are? Why is it important that scientists use all of their results and not just some of them? What should we do if the evidence neither supports nor contradicts the hypothesis?