False Positive HIV Test

Imagine an HIV test that is 95% accurate (false positive rate of 5%) and around 2% of the tested population is infected with HIV. What is the probability that you actually have HIV when your test comes back positive?

29%

To read more about this, see the False Positive Paradox page on Wikipedia.

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Water Rebus

What does this represent?

 WATER
-------
 SWIM

Swim underwater.

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Against the Rules for You to Play Fair

It’s against the rules for you to play fair,
I always win but you don’t care,
I’ve ruined lives and crushed dreams,
But the allure is too much it seems.

What am I?

A casino. If you use methods to make the odds more fair to you, they kick you out. The house always wins, yet people continue to play. Gambling has ruined countless lives and crushed dreams of making millions, but the hope of winning continues to draw people in.

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Reflecting on Time

When a clock’s reflection is 2:30, what is the correct time?

9:30

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Lies Behind Stars

It cannot be seen, it cannot be felt,
Cannot be heard, cannot be smelt,
Lies behind stars and under hills,
And empty holes it fills.
Comes first follows after,
Ends life kills laughter.

Darkness.

Posted in Riddles

Word Jumble

Frederick takes half of CONNIE, part of NESTA, part of NELLIE and part of AUNTIE to create something new. What does he call his new creation?

Constantine

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Take Away All My Letters

Take away my first letter,
Take away my second letter,
Take away all my letters,
and I remain the same.

What am I?

A mail carrier. Even when there aren’t any letters left to deliver, they’re job is still the mail carrier.

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The Floating Cork

If a cork is placed into a glass of water, it will almost always drift to the side of the glass. There is one simple way, however, to get the cork to float in the center of the glass. What is it?

Water, the glass, and the cork are all that is required.

The reason that a cork drifts to the side of a glass is that it floats to the highest point. Since water “clings” to the glass, the highest point is around the edge of the water. To get the cork to float in the middle of the glass, all you have to do is fill the glass as much as possible. The water will form a convex shape above the glass, with the highest point at its center. This is where the cork will settle.

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A Sign in Japan

This sign was seen in Japan. What does it mean?

A sign seen in Japan

It’s a glass sign containing instructions on a glass door.
It says PULL on one side and PUSH on the opposite side.

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Working With Something In Its Eye

What always works with something in its eye?

A needle. Thread goes in the eye of the needle when you sew. If you sew…

Posted in Riddles