Logical reasoning PrepTest 154 · Section 1 · Question 19

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Errors in Reasoning

Stimulus Summary:
Lift heavy objects → Wear back belt
Study: Those who wear back belts are more likely to suffer back injuries than those who don't
Conclusion: Back belts don't help prevent injury

Answer Anticipation:
There's a massive issue with this study, and one that we've seen before—the groups weren't randomly assigned. In order to reach the conclusion here, all employees would need to be randomly assigned to a back belt group and a non-back belt group, and their injury rate would need to be measured. With how this study was done, of course those wearing back belts are the ones who have a higher back injury rate—they're the ones lifting heavy objects!

As an example, imagine a retail store. Those wearing back belts work in the warehouse, and those not are on the floor. The former group is doing the work that puts their backs in danger, so even if the back belts are helping, that group would still have a much higher back injury rate.

Answer Explanation:
This answer highlights that the two groups aren't an even mix of people at risk for back injuries, pointing out the error in the argument.

Key Takeaway:
When a study is done, make sure that it's not starting with groups that have already been non-randomly determined—here, the groups were those who wear the back belts (and thus lift heavy objects) and those who don't. In order to get a valid comparison between the groups, we'd need to have a random assignment—for example, divide the warehouse workers in half, and have half use a back belt.

Incorrect. The injury rate was compared between only employees at Flegco, so even if Flegco has employees more likely to wear belts, those employees are still getting injured at a higher rate than their non-belt wearing coworkers.

Incorrect. The conclusion is that back belts don't help to prevent injury, not that they causally contribute to injury, so this answer doesn't describe the argument.

Incorrect. First, the argument doesn't make a claim that something doesn't causally contribute to a certain effect. Second, it concludes that something doesn't causally contribute to preventing that effect. Both halves of this answer choice are wrong.

Incorrect. There's no factor presented as sufficient to produce a certain effect—and even if you viewed the argument as treating the back belt as sufficient to produce increased rates of back injury, there's no indication that the argument thinks or treats it as a necessary condition for those injuries.