Determine what value of a allows for largest probability

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Homework Help Overview

The discussion revolves around determining the value of 'a' that allows the function f(x) = |x^x - x^a| to serve as a probability density function (PDF) with the largest probability of a random variable 'x' falling within two standard deviations of the mean. Participants are exploring the conditions under which this function qualifies as a PDF and the implications for the value of 'a'.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the challenges of integrating the function over a set interval to determine if it meets the criteria for a PDF. There are attempts to find x-intercepts and evaluate integrals, with some expressing uncertainty about manual methods. Others suggest numerical estimation as a potential approach to identify values of 'a'.

Discussion Status

The conversation is ongoing, with some participants sharing their numerical findings and methods, while others are questioning the mathematical rigor of their approaches. There is a recognition that visual tools, like graphing calculators, can aid in understanding the behavior of the function, but no consensus has been reached on the best method to solve the problem.

Contextual Notes

Participants note the difficulty in finding definite integrals for the function and the need for specific values of 'a' to analyze the probability within the defined range. There is mention of homework constraints that may limit the approaches available to participants.

Saracen Rue
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Homework Statement


There are two possible solutions for 'a' for which ##f(x)=|x^x-x^a|## is a probability density function. Determine the value for a which produces a PDF with the largest probability of random variable 'x' falling within two standard deviations either side of the mean.

Homework Equations


Just the rules to do with determining if function is a PDF using integrals as well as finding the mean, variance and standard deviation.

The Attempt at a Solution


I'm honestly at a loss here. There's no way to find the definite integral of this function meaning we need to integrate over a set interval. I calculated the x-intercepts to be 1 and a. I tried getting my calculator to solve (for a) ##∫_0^1f(x)dx=1## and ##∫_0^af(x)dx=1##, both individually and simultaneously, but my calculator kept giving me an error. I'm really not sure what to do here - is there a way to do this manually that I don't knoe about? Any help is greatly appreciated :)
 
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As first step I would try to numerically estimate where these values of a are.
I found one so far, I'm not so sure where to look for the other one.
 
mfb said:
As first step I would try to numerically estimate where these values of a are.
I found one so far, I'm not so sure where to look for the other one.
Thank you for your help - I had considered just brut forcing it by au substituting different values of a in but I had assumed there was an easier way to do it. I used an online graphing calculator to hell me visualise what was going on and to know where to look for the values of a. If you wouldn't mind could you please look over my working out for this? Here's the link: https://www.desmos.com/calculator/68gbrixyqf
Note, I defined to different functions for each value of a while I was working this out to keep better track of things. I very much appreciate you spending your time to help :)
 
Maybe the whole question asks for a numerical analysis. Just by eye I'm quite sure I know which one has a larger integral within 2 standard deviations, but that is not a very mathematical approach.
 

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