Math Problem Statement

Determine the standard deviation of the sampling distribution, and calculate the probability that more than 41% of a sample of 600 adults do not own a credit card.

Solution

From the image you provided, it appears you are working on a statistics problem related to sampling distributions. Let's break it down step by step.

Problem Overview:

  1. Scenario:

    • 37% of adults do not own a credit card.
    • A simple random sample of 600 adults is obtained.
  2. Questions:

    • (a) Find the standard deviation of the sampling distribution of the sample proportion p^\hat{p}.
    • (b) Find the probability that more than 41% of the sample do not own a credit card.
    • (c) Interpret the probability from part (b) and estimate the expected number of samples where more than 41% do not own a credit card in 100 random samples.

Let's work through it:

Part (a): Standard Deviation of the Sampling Distribution of p^\hat{p}

The formula for the standard deviation (often called the standard error) of the sampling distribution of the sample proportion p^\hat{p} is:

σp^=p(1p)n\sigma_{\hat{p}} = \sqrt{\frac{p(1 - p)}{n}}

Where:

  • p=0.37p = 0.37 (the population proportion of adults who do not own a credit card),
  • n=600n = 600 (the sample size).

Now, let's compute that:

σp^=0.37(10.37)600=0.37×0.63600\sigma_{\hat{p}} = \sqrt{\frac{0.37(1 - 0.37)}{600}} = \sqrt{\frac{0.37 \times 0.63}{600}}

I'll calculate that next.The standard deviation of the sampling distribution of p^\hat{p} is approximately 0.020 (rounded to three decimal places).

Part (b): Probability that more than 41% of the sample do not own a credit card

To find this probability, we first convert the proportion to a z-score using the formula:

z=p^pσp^z = \frac{\hat{p} - p}{\sigma_{\hat{p}}}

Where:

  • p^=0.41\hat{p} = 0.41,
  • p=0.37p = 0.37,
  • σp^0.020\sigma_{\hat{p}} \approx 0.020.

I'll calculate the z-score and then find the probability using the standard normal distribution.The z-score is approximately 2.03. Now, let's find the probability of getting a z-score greater than 2.03 using the standard normal distribution table (or a calculator). This corresponds to the area to the right of z=2.03z = 2.03.

We can use a standard normal distribution to find this value.The probability that more than 41% of the sample do not own a credit card is approximately 0.0212 (or 2.12%).

Part (c): Interpretation and estimation for 100 random samples

Given that the probability is about 2.12%, we expect about 2.12% of the 100 random samples to result in more than 41% of adults not owning a credit card. To estimate this:

Expected number of samples=100×0.0212=2.12\text{Expected number of samples} = 100 \times 0.0212 = 2.12

Rounding to the nearest integer, we expect about 2 samples.


Would you like further clarification or additional details on any part? Here are some related questions to explore:

  1. How would the standard deviation change if the sample size were increased?
  2. What does a z-score of 2.03 imply in terms of the distribution?
  3. What would be the probability if we asked about less than 41% of the sample not owning a credit card?
  4. How do we interpret the sampling distribution of proportions in real-world contexts?
  5. If the population proportion were different, how would that impact the probability calculation?

Tip: Always check the context of proportions in statistics, especially in large samples. Small changes can have a significant impact on the probabilities.

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Math Problem Analysis

Mathematical Concepts

Sampling distribution
Standard deviation
Proportions
Z-scores
Probability

Formulas

Standard deviation of the sample proportion: σ̂p = sqrt((p(1 - p)) / n)
Z-score formula: z = (p̂ - p) / σ̂p

Theorems

Central Limit Theorem

Suitable Grade Level

College level (Introductory statistics)