Calculating Probability for Test Scores: Mean 2.725, SD 1.329, 61 Students

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Discussion Overview

The discussion revolves around calculating the probability that a group of 61 students achieves an average test score of at least 3, given a mean score of 2.725 and a standard deviation of 1.329. The context includes statistical concepts such as the Central Limit Theorem (CLT) and Chebyshev's Inequality, with a focus on probability distributions and their applications in this scenario.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • One participant suggests assuming a normal distribution for the test scores and inquires if others have learned how to find probabilities in such distributions.
  • Another participant emphasizes the use of the Central Limit Theorem to calculate the probability of the average score being at least 3, indicating the need to find the sampling distribution of the average score.
  • One participant proposes using Chebyshev's Inequality to set up a solution, providing the formula and noting the values for mean and standard deviation.
  • A participant points out the distinction between the probability of the average score and the percentage of individual scores, questioning how the number of students affects the problem.
  • A later reply seeks clarification on the implications of the number of students and whether Chebyshev's Inequality is a valid approach for solving the problem.

Areas of Agreement / Disagreement

Participants express varying approaches to solving the problem, with no consensus on the best method or the interpretation of the question. Some focus on the normal distribution and CLT, while others consider Chebyshev's Inequality, indicating multiple competing views remain.

Contextual Notes

Participants have not reached a resolution on the assumptions regarding the distribution of scores or the applicability of different statistical methods, leaving the discussion open-ended regarding the best approach to calculate the desired probability.

monacom08
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Statistics Need Help !1

I am doing review for a test and i still can not get this problem..HELP Please

The scores on a test had a mean of 2.725 and a standard deviation of 1.329. A teacher had 61 students take the test. Although the students were not random sample, the teacher considered the students to be typical of all the national students. what us the probability that the students achieved an average score of at least 3?

Please help!
 
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I'm going to assume that the distribution is a normal distribution.

Have you studied how to find probabilities in a normal distribution? Have you learned about finding probabilities in a standardized normal distribution (ie mean = 0, std dev = 1)? Do you know how to convert your distribution to a standardized normal distribution?
 


The point of monacom08's problem is to use the CLT to calculate

<br /> P(\overline X \ge 3) = 1 - P(\overline X &lt; 3)<br />

so the first step is to find the sampling distribution of \overline X.
 


Try setting up a solution using Chebycheff's Inequality:

P(|Y - µ| >= kσ) <= 1/k^2

We know that µ is the mean, which equals 2.725, and that σ is the square root of variance (i.e., the standard deviation, which is 1.329).
 


Look at this part of the problem: "what us the probability that the students achieved an average score of at least 3? "

The question asks about the chance the average score is a certain size, not the percentage of individual scores that are a certain size.
 


statdad said:
The question asks about the chance the average score is a certain size, not the percentage of individual scores that are a certain size.

Is this in regards to what I wrote? I am very much a neophyte of statistics, especially compared to you, but how does the number of students and the idea of a percentage achieving an average located above a certain number change the problem? Is Chebysheff's Inequality a viable means to a solution?
 

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