Police chief: During my tenure as chief, crime in this city has fallen by 20 percent. This is clearly the result of m...

on December 6, 2019


I didn't choose D because we were warned not to compare percentages fro two different categories (the whole country and the police chiefs' precinct) if we don't know the know the actual numbers. Although that may not apply to this question because we don't have specific counts of how many crimes were stop, can you please explain in more detail how the overall crime rate dropping calls into question the police chiefs statment?


Ben on December 6, 2019

Hi Tomgbean, thanks for the question!

You make a good point, that when given two percentages, we shouldn't compare them to draw any conclusions about which signifies a greater absolute quantity.

However, this question is an offshoot of a numbers/percentage idea. By showing that the crime rate reduced by 30% in the country as a whole, this calls into question the police chief's conclusion that the 20% crime reduction in his city due to his strategy. We can ask the very logical question, "if your strategy is so effective, such that you can say the reduction is due to the strategy itself, then how come your city's crime reduction is less than the country as whole?"

The logic that he employs some special strategy which reduces crime rate in his city would be more plausible had his city's crime rate reduction been significantly greater than the country as a whole. But with a greater crime reduction in the country as a whole, his strategy seems ineffective.

I hope this helps. Please let me know if you have any other questions!

on December 7, 2019

Thanks, Ben! It helps.

Ravi on January 14, 2020

@tomgbean, let us know if you have any other questions!

on June 19, 2020

Thank you for this explanation!

Ben on June 28, 2020

@Saskipper, you are very welcome!