Question

Give null and alternative hypotheses for a population proportion, as well as sample results. Use StatKey or other technology to generate a randomization distribution and calculate a p-value. StatKey tip: Use "Test for a Single Proportion" and then "Edit Data" to enter the sample information. Hypotheses: \(H_{0}: p=0.5\) vs \(H_{a}: p<0.5\) Sample data: \(\hat{p}=38 / 100=0.38\) with \(n=100\)

Short answer

The null and alternative hypotheses are \(H_{0}: p = 0.5\) and \(H_{a}: p < 0.5\) respectively. The sample data provides a sample proportion of \(\hat{p}=38/100 = 0.38\) based on a sample size \(n=100\). This data can be used on statistical software like StatKey to generate a random distribution and compute the p-value.

Step-by-step solution

Hypothesis Formulation

The null hypothesis \(H_{0}\) posits that the population proportion \(p = 0.5\). The alternative hypothesis \(H_{a}\) suggests that the population proportion \(p < 0.5\). It's essential to remember that the null hypothesis often includes an equals sign.

Sample Data Interpretation

Our sample proportion is given by \(\hat{p}=38/100 = 0.38\). This is based on a sample size \(n=100\). The sample implies that in 100 trials, the predicted scenario occurred 38 times.

Use of Statistical Software

With our hypotheses and sample data, we can now use StatKey or compatible software to conduct our tests. Select 'Test for a Single Proportion' then 'Edit Data' where you insert your sample data.

Calculation of p-value

Using the software, generate a random distribution. The p-value can be subsequently calculated. The p-value is the chance of obtaining our observed sample data (or more extreme) assuming that the null hypothesis is true. It measures the strength of evidence in support of a null hypothesis.

Key concepts

Null and Alternative Hypotheses

Understanding null and alternative hypotheses is a cornerstone of hypothesis testing. In any experimental setup, a null hypothesis (\(H_{0}\)) is a statement that there is no effect or no difference, and it specifies a population proportion that we assume to be true before collecting any data. In contrast, the alternative hypothesis (\(H_{a}\) or \(H_{1}\) ) is a statement that indicates what we suspect might be true instead.

Using the example from the exercise, the null hypothesis is \(H_{0}: p=0.5\) suggesting no difference from the expected value. The alternative hypothesis, \(H_{a}: p<0.5\) in this case, suggests that the actual population proportion is less than what we initially believed. Accurately formulating these hypotheses is essential for analyzing the direction and the robustness of the evidence provided by the sample data.

Population Proportion

The term population proportion, denoted by \(p\) indicates the likelihood of a particular outcome within a population. In hypothesis testing, we use the sample proportion (\(\hat{p}\) as an estimate of the true population proportion based on the sample data. The sample proportion is calculated by dividing the number of times the event of interest occurs by the total number of trials.

In the context of the textbook exercise, the sample proportion was calculated to be \(\hat{p}=38/100=0.38\) from a sample size of 100. This estimate plays a pivotal role in testing our hypotheses and determining the statistical significance of our findings.

P-value Calculation

P-value calculation is a crucial step in hypothesis testing that quantifies the evidence against the null hypothesis. The p-value is the probability of observing a sample statistic as extreme or more extreme than the one calculated from the sample data, given that the null hypothesis is true.

The smaller the p-value, the stronger the evidence against the null hypothesis. A commonly used threshold for significance is \(p < 0.05\) which indicates that if the null hypothesis were true, there would be less than a 5% chance of observing a result as extreme as the sample data. Calculating the p-value allows researchers to make an informed decision on whether to reject the null hypothesis in favor of the alternative.

StatKey Software

To streamline the process of hypothesis testing, tools like StatKey software are invaluable. StatKey is designed to conduct statistical tests, including hypothesis testing for a single proportion, and create the relevant distributions for analysis. The user-friendly interface allows for easy entry of sample data, and it automates the randomization process and the calculation of the p-value.

Following the steps in the provided exercise, StatKey simplifies these processes by allowing the user to input their sample information directly and obtain results that guide decision-making in statistical testing. By promptly generating a randomization distribution and the associated p-value, the software aids in substantiating the statistical reasoning.

Randomization Distribution

A randomization distribution is a representation of what the distribution of a sample statistic (like a sample proportion) would look like, assuming the null hypothesis were true. This distribution is generated by randomly reassigning outcomes among the observations in the sample and calculating the statistic for many randomized samples.

The central purpose of observing a randomization distribution is to determine how unusual the observed statistic is. The extremity of the sample data is assessed in the context of the distribution, which culminates in the calculation of the p-value. By comparing the sample statistic to this distribution, we essentially determine the likelihood of obtaining our sample or more extreme results, should the null hypothesis hold true. The randomization test is a non-parametric method of hypothesis testing which does not rely on underlying population distributions, making it versatile and robust for a range of data.