High School

A probability distribution has a mean of 57 and a standard deviation of 1.4. Use Chebychev’s theorem to find the value of c that guarantees the probability is at least 96% that an outcome of the experiment lies between 57 - c and 57 + c. (Round the answer to the nearest whole number.)

Answer :

To solve this problem, we will use Chebychev's Theorem. Chebychev's Theorem provides a way to find the minimum probability that a random variable lies within a certain number of standard deviations from the mean. The theorem states that for any distribution with mean [tex]\mu[/tex] and standard deviation [tex]\sigma[/tex], the probability that a random variable is within [tex]k[/tex] standard deviations from the mean is at least [tex]1 - \frac{1}{k^2}[/tex].

Given:

  • Mean ([tex]\mu[/tex]) = 57
  • Standard deviation ([tex]\sigma[/tex]) = 1.4
  • Desired probability = 96% or 0.96

The problem asks us to find the value of [tex]c[/tex] such that the probability of an outcome lying between [tex]57 - c[/tex] and [tex]57 + c[/tex] is at least 96%. According to Chebychev's Theorem:

[tex]1 - \frac{1}{k^2} = 0.96[/tex]

Solving for [tex]k[/tex]:

  1. [tex]1 - \frac{1}{k^2} = 0.96[/tex]
  2. [tex]\frac{1}{k^2} = 1 - 0.96 = 0.04[/tex]
  3. [tex]k^2 = \frac{1}{0.04} = 25[/tex]
  4. [tex]k = \sqrt{25} = 5[/tex]

The value of [tex]k[/tex] is 5. This means that to guarantee at least 96% probability, the outcomes should lie within 5 standard deviations from the mean.

Now, calculate [tex]c[/tex] using the relation [tex]c = k \times \sigma[/tex]:

[tex]c = 5 \times 1.4 = 7[/tex]

Therefore, the value of [tex]c[/tex] should be 7, rounding to the nearest whole number.

Thus, the outcome of the experiment will lie between [tex]57 - 7 = 50[/tex] and [tex]57 + 7 = 64[/tex] with at least 96% probability.