#20 - TV meteorologist: Our station’s weather forecasts are

[alee]

Hi guys,

I have a question about Q20, Prep Test 55 Section 4. It's a Strengthen Question, and the conclusion to be stregthened is that:
'our station's weather forecasts are more useful and reliable than those of the most popular new station in the area'.

Why is the answer (A) ('The meterologists station forecast rain more oftn than did the most popular new station in the area')?

Are we to interpret 'forecast rain' to mean 'provide the service of forecasting whether there will be rain or not' (1) or 'number of times we forecast that there will be rain' (2)?

In the case of (1), I see how it strengthens the conclusion, since it suggest that the meteorologists station provides the service more frequently than the most popular new station.

However, the phrasing of option (A) suggests interpretation 2, so I am very confused.

Could you please help to clarify? That would be great!

[Steve Stein]

Thanks for your question--that actually comes from Prep Test 54.

The meteorologist's conclusion is that the station's forecasts are more useful and reliable than the others'. The right answer choice will be the one that strengthens this claim of forecast usefulness and reliability.

The meteorologist mentions in the stimulus that the station's forecasts have been right the majority of the time--so, they're right for the majority of their forecasts, but we don't know anything about the actual number of correct forecasts they've made.

But if, as correct answer choice A provides, they have also made more forecasts than the other station, then this strengthens their case for greater usefulness and reliability (since it is also true that the majority of their rain forecasts are accurate).

Kind of a tricky numbers and percentages question--let me know whether that clears this one up--thanks!

~Steve

[alee]

Thanks Steve,

Your replies have been awesome. Just to get this one straight, so what you mean is that there is a kind of gap in the argument in that even if 'on most occasions that they have predicted rain, they have been right', it could also be the case that they (for example) just forecasted this to happen 3 times, and got it right 2 times, whereas their competitors got it right less than 2/3 of the the time, but provide far more frequent forecasts (say 100 forecasts, with 65 correct ones)

This would undermine the *usefulness* part of the conclusion. However, option (A) 'seals' that gap by ruling out this possibility and in fact adding the information that the station forecast rain more times than its competitor.

Have I understood your explanation correctly?

[Steve Stein]

Hi Alee,

You've got it--in fact, I was going to use those exact numbers to exemplify the idea that percentage by itself provides very limited information.

..and I'm really glad that you've found the forum helpful!

~Steve

[Barcelona10]

June 2008, LR Sec. 4, # 20 STRENGTHEN: (on weather forecasting) The answer A is the correct answer, but based on my interpretation, I thought it would Weaken. If, as answer A says, the meteorologist’s station forecasts rain more often than other news stations in areas, it seems to suggest that there is the possibility that the meteorologist’s station is getting their forecast for rain simply because they forecast it so much. It might rain 10 days in a year, but if we forecast rain 365 days, then though one may boast that they predicted all rain dates correctly, they wouldn’t be very reliable or useful since they got so many other rain forecasts incorrect. But this contradicts A. How do you approach this question mechanistically?

[Steve Stein]

Hey Barcelona10,

That's a good question. Without any additional information, you would be right--correctly forecasting rain more often than your competitors is not that impressive if that's your forecast every day.

In this case, however, the stimulus has provided that they are also right most of the time, which is a claim that the station's competitors cannot make. So, with the new information provided by this answer choice, we can now say that not only do they forecast rain more often than their competitors, they are also right most of the time--that means that they have a greater number of accurate rain forecasts than the others, and their percentage is better than their competitors--this makes for a pretty strong argument.

I hope that's helpful! This can be a tough one--please let me know whether this is clear--thanks!

~Steve

[Barcelona10]

Thank you very much for the reply! I do have a follow up question if you're willing to answer: How does A strengthen? So, now I know that the percentage of accurate forecasts is greater for the meteorologist's station. (A) says the station forecast rrain more often than did the most popular news station in the area. Is this not just restating the premises, and therefore, not really doing anything to the argument. I guess what I'm not seeing is what (A) adds to the argument...

[Steve Stein]

Thanks for your response!

The stimulus provides that the station's rain forecasts are accurate most of the time, and that they are the only station that can make this claim.

That's great, but what if they only have one rain forecast per year? 100% accuracy is not all that impressive if the numbers aren't there.

So, the stimulus provides that they are the only ones that are right most of the time, and the correct answer choice provides that they also have more rain forecasts than their competitors. Putting these two together, they have the best percentage and the most rain forecasts.

I hope this is helpful--please let me know whether this is clear--thanks!

~Steve

[Haleyeastham]

Can you please explain to me how answer choice A is correct?

Thank you!

[Robert Carroll]

Haley,

The meteorologist says not that the station has been right most of the time in general, but most of the time "when we have forecast rain for the next day." We don't know how often that's happened - if it hasn't happened very often (in other words, they haven't forecast rain very often), then all we know is that the station has been right in a majority of a small number of cases. Thus, information about how often they've made the forecast would help out here. If they've made that forecast more often than the most popular news station in the area, and that station has not been correct in a majority of cases when that station has made the same forecast (last sentence!), then the meteorologist's station is known to have been correct in a majority of cases where one competitor was less correct (because they were wrong at least half the time, by the last sentence).

Robert Carroll