TransMarket Group LLC
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www.transmarketgroup.com 150 to 499 Employees

# TransMarket Group LLCJunior Trader Interview Question

I interviewed in Chicago, IL and was asked:
"Suppose there's a 60% chance of rain on saturday, and a 80% chance of rain on sunday. Given that it rained over the weekend, what's the chance it rained saturday?"

Part of a Junior Trader Interview Review - one of 42 TransMarket Group LLC Interview Reviews

1
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Use Baye's formula:
b=p(rain over weekend)=1-p(no rain over weekend)= 1-(.4*.2)=.92

a=(p rain on saturday)=.6
p(b given a)= 1 since if it rained on sautrday, it had to rain overhe weekend
so p(a)*p(b given a)/p(b)=.6/.92=.65=p(a given b)=p( rain on saturday given it rained on the weekend)
- Anonymous on May 28, 2012 Flag Response
0
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0.65 > 0.5 dude... think again
- Anonymous on Jan 26, 2013 Flag Response
1
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The first answerer is correct I think.

One of the following happened:

It rained on Saturday only: 0.6 * 0.2 = 0.12
It rained on Sunday only: 0.4 * 0.8 = 0.32
It rained on Saturday and Sunday: 0.6 * 0.8 = 0.48

Add these up: 0.92 total of it raining over the weekend.

But the question is stated that it's given that it rained over the weekend. So:

Pr(Saturday) = (0.12 + 0.48) / 0.92 = 0.6 / 0.92 = .652 (roughly 2/3)
- Anonymous on Jul 20, 2013 Flag Response