Question

In Exercises 6.1 to \(6.6,\) if random samples of the given size are drawn from a population with the given proportion, find the standard error of the distribution of sample proportions. Samples of size 30 from a population with proportion 0.27

Short answer

The standard error of the distribution of sample proportions is approximately 0.089.

Step-by-step solution

Understand and note down given parameters

The provided proportion of the population (\( p \)) is 0.27 and the sample size (\( n \)) is 30.

Substitute the values into the standard error equation.

Now we have to place these provided values into the standard error equation, which is \( \sqrt{\frac{p(1 - p)}{n}} \). So now it becomes \( \sqrt{\frac{0.27(1 - 0.27)}{30}} \)

Perform the calculation

Upon performing the calculation, the standard error becomes approximately 0.089.

Key concepts

Sample Proportions

Understanding sample proportions is essential when working with statistical sampling. A sample proportion is a decimal value that represents the fraction of items in a sample that have a certain trait. For instance, let's say we want to know the proportion of left-handed students within a school. If we survey a class of 30 students and find that 9 are left-handed, the sample proportion (\( \text{denoted as} \( \(\hat{p}\) \) \)) would be the number of left-handed students (9) divided by the total number of surveyed students (30), resulting in a sample proportion of 0.30.

In the context of our exercise, we are dealing with a sample of size 30, and we want to estimate the population proportion of a certain characteristic that is present at 0.27 rate. Understanding the variability or precision of this estimate is where the standard error comes into play, which we calculate from the sample proportion.

Population Proportion

The population proportion (\( p \) is an underlying value which represents the ratio of members in a population who have a particular characteristic. Considering our original problem, the population proportion (0.27) suggests that if we could look at every member within the population, 27% of them would have the characteristic we are interested in.

When studying a whole population is not feasible, we use samples to estimate population parameters like proportion. However, we must acknowledge that every sample we take is subject to sampling variability, which leads us to estimate the standard error to quantify the uncertainty of our sample proportion as an estimate of the true population proportion.

Standard Error Equation

The standard error equation is crucial for understanding the variability of an estimate from sample data. It helps us understand how tightly clustered or spread out the sampling distribution of our estimate might be. It is calculated using the formula \(\sqrt{\frac{p(1 - p)}{n}}\), where \(\(p\)\) is the population proportion, and \(\(n\)\) is the sample size.

In the exercise, we're given the population proportion of 0.27 and a sample size of 30. Plugging these values into the standard error formula provides us with an estimate of how much we expect our sample proportion to deviate from the population proportion due to random sampling alone. The lower the standard error, the better our estimate typically is, because it indicates less variability or uncertainty in our sample proportion.

Statistical Sampling

Statistical sampling involves selecting a subset of individuals from within a larger population to estimate characteristics about the whole group. The key is that the sample must be random and representative of the population in order to provide reliable estimates. If it is not, the results could be biased.

In exercises like the one we’ve examined, where we are given sample sizes and population proportions, we are implicitly operating under the assumption of random sampling. The concept of standard error is inherently linked to this practice; it quantifies the expected fluctuation of sample statistics if we were to repeat our sampling process many times. It’s a tool that tells us about the reliability of our sample-based estimates and, by extension, the quality of our statistical conclusions.