Math Problem Statement

The Higher Education Research Institute at UCLA collected data from 203,967 incoming first-time, full-time freshmen from 270 four-year colleges and universities in the U.S. 71.6% of those students replied that, yes, they believe that same-sex couples should have the right to legal marital status. Suppose that you randomly pick twelve first-time, full-time freshmen from the survey. You are interested in the number that believes that same-sex couples should have the right to legal marital status.

What is the standard deviation (𝜎)? (Round your answer to four decimal places.) 𝜎 =

Solution

This is a binomial probability problem, where we are interested in the standard deviation of a binomial distribution. The binomial distribution has the following properties:

  • nn: number of trials (in this case, 12 freshmen)
  • pp: probability of success (in this case, the probability that a student believes same-sex couples should have the right to legal marital status, which is 0.716)
  • q=1pq = 1 - p: probability of failure (i.e., the complement of the success probability, q=10.716=0.284q = 1 - 0.716 = 0.284)

The standard deviation σ\sigma for a binomial distribution is given by the formula:

σ=npq\sigma = \sqrt{n \cdot p \cdot q}

Step-by-step calculation:

  1. n=12n = 12
  2. p=0.716p = 0.716
  3. q=10.716=0.284q = 1 - 0.716 = 0.284

Now, plug these values into the formula:

σ=120.7160.284\sigma = \sqrt{12 \cdot 0.716 \cdot 0.284}

First, calculate the product inside the square root:

120.7160.284=2.441112 \cdot 0.716 \cdot 0.284 = 2.4411

Then, take the square root:

σ=2.4411=1.5623\sigma = \sqrt{2.4411} = 1.5623

Thus, the standard deviation σ\sigma is approximately 1.5623.

Would you like any additional details or clarifications?

5 Related Questions:

  1. How do you calculate the mean of a binomial distribution?
  2. What is the probability that exactly 8 out of the 12 students support same-sex marriage rights?
  3. How would the standard deviation change if the sample size were increased to 20 students?
  4. What assumptions must hold true for a distribution to be modeled as binomial?
  5. How can the normal approximation be used for a binomial distribution?

Tip:

For binomial distributions with large nn and probabilities close to 0.5, you can use the normal approximation for faster calculations.

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Math Problem Analysis

Mathematical Concepts

Binomial Distribution
Probability
Standard Deviation

Formulas

Standard deviation for binomial distribution: σ = √(n * p * (1 - p))

Theorems

Binomial Theorem

Suitable Grade Level

Grades 10-12