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Give information about the proportion of a sample that agree with a certain statement. Use StatKey or other technology to find a confidence interval at the given confidence level for the proportion of the population to agree, using percentiles from a bootstrap distribution. StatKey tip: Use "CI for Single Proportion" and then "Edit Data" to enter the sample information. Find a \(99 \%\) confidence interval if, in a random sample of 1000 people, 382 agree, 578 disagree, and 40 can't decide.

Short Answer

Expert verified
To find the 99% confidence interval for the proportion, the sample proportion will first be calculated as \( p̂ = 0.382 \). Then, a bootstrap method will be applied to generate an empirical approximation of the sampling distribution of \( p̂ \). The 0.005th and 0.995th percentiles of this bootstrap distribution will serve as the lower and upper bounds of the confidence interval, respectively. Interpretation: We are 99% confident that the true proportion of the population that agrees to this statement lies within this calculated confidence interval.

Step by step solution

01

Identify given data

Firstly, take note of the given data in the problem. The sample size \( n \) is 1000. The number of people who agree, designated as \( x \), is 382. The confidence interval that we want to find is \( 99\% \). This leaves \( 1\% \) remaining, split into two tails of our distribution, giving us \( 0.005 \) in each tail.
02

Calculate the sample proportion

Calculate the sample proportion (p̂) using the formula \( p̂ = \frac{x}{n} \). So, \( p̂ = \frac{382}{1000} = 0.382 \). The sample proportion signifies the percentage of individuals in the sample who agree with the statement.
03

Use bootstrap method for confidence interval

Now, conduct a bootstrap method for obtaining the confidence interval. This is done by generating a large number of resamples of size \( n \) with replacement from the original sample. Calculate the proportion for each resample and draw a histogram. Locate the data points that correspond to the 0.005th percentile and the 0.995th percentile. These percentiles make up the \( 99\% \) confidence interval.
04

Interpret the result

The calculated confidence interval is the likely range of the true population proportion, indicating that we are 99% confident that the true proportion of the population that agrees to this statement lies within this confidence interval. If the confidence interval contains values that make a practical difference in the interpretation of the situation, we might say the findings are statistically significant.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Bootstrap Method
The Bootstrap Method is a powerful statistical tool used to estimate the variability of a statistic like the mean or proportion. This technique involves repeatedly resampling, with replacement, from an observed dataset to create a range of "synthetic" datasets. By doing this many times, typically thousands or even tens of thousands of times, we can construct a distribution of the sample statistic, which is the bootstrap distribution.

This method is particularly useful when dealing with proportions, such as when we want to construct a confidence interval. By simulating numerous sets of data, we can use the percentiles of these simulations to estimate the bounds of our confidence interval.@The calculations start with drawing random samples from the original dataset (in this case, 1000 people where 382 agree with a statement). For each sample drawn, we calculate the sample proportion (the proportion of people who agree).@Over many simulated trials, we can construct a distribution of these sample proportions, from which we can derive the confidence interval. This bypasses the need for an analytically derived formula, making the Bootstrap Method straightforward, especially when traditional assumptions about the data distribution do not hold.
Sample Proportion
The concept of Sample Proportion is foundational in statistics, especially when analyzing binary outcomes. Sample proportion, denoted as \( \hat{p} \), is a gauge of the proportion in the sample that exhibits a particular trait or behavior. It's calculated using the formula \( \hat{p} = \frac{x}{n} \), where \( x \) is the number of successes (such as people agreeing in a survey) and \( n \) is the total number of observations (the total number of survey participants).

For example, in our given exercise, the sample size \( n \) is 1000, and the number of people agreeing \( x \) is 382. Plugging these numbers into our formula leads to \( \hat{p} = \frac{382}{1000} = 0.382 \). This result means that 38.2% of the sample agrees with the statement.

The sample proportion is crucial because it serves as the point estimate of the population proportion, around which we construct our confidence interval. It gives us an initial understanding of how prevalent a particular opinion or characteristic is within our sample, which helps in making broader inferences about the larger population.
Statistical Significance
Statistical Significance is a concept used to determine if the result of an analysis has enough evidence to infer a meaningful conclusion for the population from which the sample is drawn. When dealing with proportions, this often relates to determining whether the calculated confidence interval includes or excludes certain values that hold practical importance.

In relation to confidence intervals, if an interval does not include a specific value of interest (such as 0 or 0.5), it might suggest that the observed effect or proportion is statistically significant. This means it's unlikely to have occurred due to random chance alone.

For our exercise, if the confidence interval for the sample proportion of people who agree doesn't overlap with a value that's typically considered a baseline or non-significant level, it can imply that the observed agreement proportion is not just due to random variation. This has practical relevance, helping us to conclude with a certain level of confidence (in this case, 99%) that the observed proportion is reflective of the underlying population dynamics beyond random variance.

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Give information about the proportion of a sample that agrees with a certain statement. Use StatKey or other technology to estimate the standard error from a bootstrap distribution generated from the sample. Then use the standard error to give a \(95 \%\) confidence interval for the proportion of the population to agree with the statement. StatKey tip: Use "CI for Single Proportion" and then "Edit Data" to enter the sample information. In a random sample of 100 people, 35 agree.

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