What is the probability that the proportion of voters in …

Mathematics Questions

A polling agency is investigating the voter support for a ballot measure in an upcoming city election. The agency will select a random sample of 500 voters from one region, Region A, of the city. Assume that the population proportion of voters who would support the ballot measure in Region A is 0.47. What is the probability that the proportion of voters in the sample of Region A who support the ballot measure is greater than 0.50

Short Answer

The problem involves a sample size of 500 with a population proportion of 0.47. After calculating the mean and standard deviation, the probability that the sample proportion exceeds 0.50 is found to be approximately 0.089264 using the z-score method.

Step-by-Step Solution

Step 1: Understand the Given Data

In the problem, we are provided with several important details necessary for calculating the desired probability. Specifically:

  • Sample Size (n): 500
  • Population Proportion (p): 0.47

These values will be used to calculate the mean and standard deviation of the sampling distribution to help find the probability.

Step 2: Calculate the Mean and Standard Deviation

The next step involves calculating the mean and the standard deviation of the sampling distribution using the formulas:

  • Mean ((mu_x)): (mu_x = p = 0.47)
  • Standard Deviation ((sigma)): (sigma = sqrt{frac{p(1-p)}{n}} = sqrt{frac{0.47(1-0.47)}{500}} = 0.0223)

These calculations are vital as they will be used in determining the probability that the sample proportion exceeds 0.50.

Step 3: Find the Required Probability

We can now compute the probability that the sample proportion (P(X > 0.50)) using the z-score formula:

  • Z-Score Calculation: (P(X > 0.50) = Pleft(frac{X – mu}{sigma} > frac{0.50 – 0.47}{0.0223}right) = P(Z > 1.3453))
  • Z-Table Value: The area under the normal curve to the left of (Z = 1.3453) gives us (P(Z > 1.3453) = 0.089264)

Thus, the final result for the probability that more than 50% of the sample supports the measure is (P(X > 0.50) = 0.089264).

Related Concepts

Sample Size (N)

The number of observations in a sample, which affects the accuracy of statistical calculations and estimates

Population Proportion (P)

The percentage of a particular characteristic within the total population being studied, used to estimate the sample characteristics

Z-Score

A statistical measure that describes a value’s relation to the mean of a group of values, calculated by subtracting the mean from the value and dividing by the standard deviation, used to determine probabilities in a normal distribution.

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