Math Problem Statement

A population of values has a normal distribution with and . If a random sample of size is selected,

Find the probability that a single randomly selected value is greater than 208.8. Round your answer to four decimals. P(X > 208.8) = 0.1894 Incorrect

Find the probability that a sample of size is randomly selected with a mean greater than 208.8. Round your answer to four decimals. P(M > 208.8) = 0

Solution

To solve this, we need to break it down into two separate parts:

Part 1: Probability that a single randomly selected value XX is greater than 208.8

The problem provides us with the following information:

  • The population has a normal distribution, with a given mean μ\mu and standard deviation σ\sigma.
  • We need to find P(X>208.8)P(X > 208.8), which is the probability that a randomly selected value is greater than 208.8.

Unfortunately, you did not provide the mean μ\mu and standard deviation σ\sigma of the population. I’ll assume they are missing from the problem statement you copied, and you should provide these values.

The procedure for finding P(X>208.8)P(X > 208.8):

  1. Standardize the value to a ZZ-score using the formula:

    Z=XμσZ = \frac{X - \mu}{\sigma}

  2. Use the standard normal distribution to find the probability associated with this ZZ-value.

  3. Subtract the cumulative probability from 1, since you want P(X>208.8)P(X > 208.8).


Part 2: Probability that a sample mean MM is greater than 208.8

For the second part of the question, where you are asked to find the probability of the sample mean being greater than 208.8, you need the sample size nn. Again, the value for nn is missing from the information provided.

In this case, we work with the sampling distribution of the sample mean, which has a mean μ\mu and a standard deviation known as the standard error of the mean, calculated as:

Standard Error (SE)=σn\text{Standard Error (SE)} = \frac{\sigma}{\sqrt{n}}

The steps to find P(M>208.8)P(M > 208.8):

  1. Standardize the sample mean to a ZZ-score:

    Z=MμSE=208.8μσnZ = \frac{M - \mu}{\text{SE}} = \frac{208.8 - \mu}{\frac{\sigma}{\sqrt{n}}}

  2. Use the standard normal distribution to find the corresponding probability.

  3. As before, subtract the cumulative probability from 1 to find P(M>208.8)P(M > 208.8).

To complete these calculations, please provide the following:

  • The population mean μ\mu
  • The population standard deviation σ\sigma
  • The sample size nn

Would you like me to proceed with any assumptions, or can you provide the missing values?


Here are 5 related questions to expand understanding:

  1. How do you calculate the standard error of the mean when the population standard deviation is known?
  2. What is the difference between the population mean and sample mean?
  3. How does the sample size affect the standard error of the mean?
  4. Why do we subtract from 1 to find P(X>value)P(X > \text{value}) in a normal distribution?
  5. How does the Central Limit Theorem justify using a normal distribution for sample means?

Tip: Always check if the problem is asking for probabilities of individual values or sample means; the approaches differ!

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Math Problem Analysis

Mathematical Concepts

Normal Distribution
Probability
Z-scores
Sampling Distribution
Standard Error

Formulas

Z = (X - μ) / σ
Z = (M - μ) / (σ / √n)
Standard Error = σ / √n

Theorems

Central Limit Theorem
Properties of the Normal Distribution

Suitable Grade Level

Grades 11-12 or Undergraduate Statistics