A consultant claims that by following his advice, an insurance-processing center can reduce the time required to process a claim for storm damage from the current average length of 6.5 to 5 workdays. ...

A consultant claims that by following his advice, an insurance-processing center can reduce the time required to process a claim for storm damage from the current average length of 6.5 to 5 workdays. He claims that his method obviously works so He says he can save the insurer further money because he can test this hypothesis by   measuring the time to process a single claim. What’s wrong with this approach?