Register to reply

Probability using box and whisker

by joel amos
Tags: probability, whisker
Share this thread:
joel amos
Jan10-13, 04:24 PM
P: 70
The question:
A box and whisker plot is made from the lengths of 39 salmon. No two lengths are the same. Two of the salmon are picked at random. What is the probability that they will both be longer than the lower quartile value.

My solution:
x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x

The x's stand for the 39 lengths. The underlined ones are (respectively) the minimum, lower quartile, median, upper quartile, and maximum. There are 29 x's above the lower quartile value (including the second x that was averaged to find that value). Therefore, the probability for the first pick would be 29/39. For the second pick, however, the quantities have been lowered by one since one salmon has already been picked. So the second probability is 28/38. When multiplied together, I got a final probability of 54.8% Is this correct, or am I somehow over-complicating the problem. What would you give as the answer?
Phys.Org News Partner Science news on
Scientists discover RNA modifications in some unexpected places
Scientists discover tropical tree microbiome in Panama
'Squid skin' metamaterials project yields vivid color display
Jan10-13, 04:48 PM
P: 12,045
I would do the same.

If 1-2% do not matter, 0.75^2 = 56.3% gives a reasonable estimate.
joel amos
Jan10-13, 04:55 PM
P: 70
Yeah, that's what a lot of people did. This was a standardized test open-ended question. I wonder which response they're looking for.

Register to reply

Related Discussions
Conditional probability - Probability of spotting a downed airplane (really basic) Set Theory, Logic, Probability, Statistics 3
Ohmic junction in Cat's-whisker detector Atomic, Solid State, Comp. Physics 2
Probability question; Conditional probability and poisson distribution Precalculus Mathematics Homework 1
[PROBABILITY] Joint probability function for two DISCRETE variables Calculus & Beyond Homework 1