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Critical Reasoning: Investigation Questions

In 2006, there were 4,736 fatalities caused by road accidents in California. That year, there were 4,810 deaths caused by motorcycle accidents nationwide. Officials in the Department of Transportation hypothesized that in 2006, it was not much safer to be a driver or a pedestrian in California than it was to be a motorcyclist anywhere in the USA.

Which of the following investigations is most likely to expose a logical flaw in the above hypothesis?



The hypothesis draws a comparison between two groups whereas this answer choice compares members of the first group only, treating it as two distinct groups: one of drivers and the other of pedestrians. 

Separating the drivers from the pedestrians would not help us discredit the hypothesis since the hypothesis addresses them as one group - drivers and pedestrians in California.

Very well done!


The hypothesis discusses how safe it is to be a member of a group or in other words - what are the chances of a member of a group to die in an accident. To compare chances, we need not only the number of deaths but also the size of the groups (4000 deaths in a group of 4000 is 100%, 4000 deaths in a group of 200,000 is 2%).

If we compare the number of deaths (casualties) in each group per 1000 people in the group we will get a ratio or chance that is comparable, such as 0.2 per 1000 or 52 per 1000. If these ratios for Californians and motorcyclists nationwide are similar then the hypothesis is true; otherwise, it's false. Either way, this is the best method for finding out.



The hypothesis compares two different groups (Californians and motorcyclists in the USA) but this answer choice suggest comparing the second group (motorcyclists in the USA) with a subgroup of itself (motorcyclists in California).

Logically, the result can only be that there are more deaths among Californian motorcyclists than there are among motorcyclists in the entire country (as one includes the other). However, this doesn't help us establish which is safer - being a Californian or being a motorcyclist in the USA.



Calculate the ratio between the fatality totals: 4,736 / 4,801 is roughly 1, which means these are similar numbers but nothing more. It is true that this similarity may have led the author to confuse total numbers with rates, but that still doesn't disprove the hypothesis.

Remember, this is not an Argument Flaw question. You are looking for an answer choice which can help prove or disprove the hypothesis depending on its results.



Since the hypothesis relates only to 2006, looking at data from previous years would not help discredit it (all it can do is prove 2006 was a relatively accident-prone or accident-free year). 

Try to pinpoint the illogical aspect of the hypothesis. There is a significant difference between the two groups that makes the hypothesis based on this comparison flawed.

Comparing the number of fatalities seperately for drivers and for pedestrians
Comparing the number of casualties in each group per 1,000 people, instead of the total number of casualties
Comparing the number of fatalities in Californian motorcycle accidents to the number of fatalities in motorcycle accidents nationwide
Calculating the ratio between the fatality totals in both groups
Comparing the 2006 statistics with statistics of previous years