# Binomial Hypothesis Test

## Calculating Probabilities Using Binomial Expansions for Hypothesis Testing

When utilizing binomial expansions for probability calculations, it is important to consider both single and cumulative values. These probabilities then play a key role in hypothesis testing, helping to determine the validity of a given hypothesis. This article will focus on the steps involved in conducting a hypothesis test for the cumulative values of a binomial distribution.

### Types of Hypotheses

Hypotheses can be divided into two categories: the null hypothesis and the alternative hypothesis. The null hypothesis assumes that any observed differences in certain characteristics of a population are due to chance. Conversely, the alternative hypothesis is what we are attempting to prove using the given data. A hypothesis test can result in two possible outcomes: acceptance of the null hypothesis or rejection in favor of the alternative hypothesis.

### Steps to Conducting a Hypothesis Test

Before delving into the steps of conducting a hypothesis test, it is important to understand several key terms:

• Critical value: The value at which we switch from accepting to rejecting the null hypothesis.
• Critical region: The region in which we reject the null hypothesis.
• Significance level: The level of accuracy being measured, typically given as a percentage. The probability of the critical value should be as close to the significance level as possible.
• One-tailed test: A test where the probability of the alternative hypothesis is either greater than or less than the probability of the null hypothesis.
• Two-tailed test: A test where the probability of the alternative hypothesis is not equal to the probability of the null hypothesis.

Now, let's take a look at the general steps involved in conducting a hypothesis test:

1. Establish a null and alternative hypothesis with relevant probabilities as given in the question.
2. Assign probabilities to the null and alternative hypotheses.
3. Write out the binomial distribution.
4. Calculate probabilities using the binomial distribution. (Hint: You do not have to use the formula. In the Casio Classwiz calculator, you can go to Menu -> Distribution -> Binomial CD and input the sample size as n, the probability as p, and the value you are trying to calculate as X).
5. Compare the calculated probability to the significance level.
6. Based on the result from Step 5, either accept or reject the null hypothesis.

### Example of a One-tailed Test

As previously mentioned, a one-tailed test is one where the probability of the alternative hypothesis is either greater than or less than the null hypothesis. For example:

A researcher wants to determine if people are able to correctly identify the difference between Diet Coke and full-fat Coke. He believes that people are simply guessing. To test this hypothesis, he randomly selects 20 people and finds that 14 of them correctly identify the difference. The researcher then conducts a hypothesis test.

a) Explain why the null hypothesis should be with the probability suggesting that they have made the correct identification.

b) Complete the test at a significance level of 5%.

SOLUTION: (Code for completing the test, using appropriate formatting)

### Example of a Two-tailed Test

In a two-tailed test, the probability of the alternative hypothesis is simply not equal to the probability of the null hypothesis. For instance:

A coffee shop offers free espresso refills. The probability that a randomly selected customer uses these refills is stated to be 0.35. A sample of 20 customers is chosen, and it is found that 9 of them have used the free refills. The researcher then conducts a hypothesis test at a significance level of 5% to determine if the probability of a randomly selected customer using the refills is different from 0.35.

SOLUTION: (Code for completing the test, using appropriate formatting)

### Critical Values and Critical Regions

As discussed earlier, critical values are the values at which we switch from accepting to rejecting the null hypothesis. Since the binomial distribution is a discrete distribution, the critical value must be an integer. While there are statistical tables in the formula booklet, they may not always be accurate for discrete distributions. Therefore, the most reliable method for finding critical values and regions is by using a calculator and testing different values until an appropriate one is found.

In conclusion, having a thorough understanding of and correctly conducting hypothesis tests is essential in making informed decisions and drawing accurate conclusions from data.

In this article, we will guide you through the process of conducting a hypothesis test and evaluating the validity of your results with confidence.

## Step 2: Understanding the Significance of Critical Values in Hypothesis Testing

When performing a hypothesis test, the critical value is the one that has a probability lower than the set significance level. It serves as a benchmark for determining the statistical significance of a study's results.

## Step 3: Defining the Critical Region in Hypothesis Testing

The critical region is the area beyond the critical value. It can be either above or below the critical value, depending on the direction of the tested hypothesis.

For example:

• A mechanic is inspecting a batch of 25 bolts to check for faulty ones. The assumption is that 30% of the bolts are faulty, but the mechanic believes the percentage is lower. In this scenario, calculating the critical value and critical region will determine the accuracy of the mechanic's belief.
• In a class of 30 students, a teacher hypothesizes that 40% of the students watch TV for two hours daily. A student disagrees, believing the percentage is either higher or lower than 40%. In this case, the critical regions must be calculated to validate the student's belief.

## The Significance of the Critical Value in Hypothesis Testing

The critical value acts as a threshold for determining whether the null hypothesis should be rejected or not. It is determined by comparing the probability of the results with half of the significance level.

## Summarizing Key Points of the Binomial Hypothesis Test

• Hypothesis testing involves using the binomial distribution to accept or reject null hypotheses.
• A null hypothesis is established before conducting a hypothesis test.
• If the data contradicts the null hypothesis, an alternative hypothesis is accepted instead.
• The critical value serves as a benchmark to determine the statistical significance of the results.
• The critical region is the area beyond the critical value.
• In a two-tailed test, there are two critical regions and two critical values.

## Determining the Sample Size for a Binomial Hypothesis Test

There is no specific sample size required for a binomial hypothesis test. Any given sample size can be used in the formula X-B(n, p) to calculate the probability values.

## The Importance of the Null Hypothesis in a Binomial Test

The null hypothesis is the belief before conducting a hypothesis test.

## The Purpose of a Binomial Test

A binomial test provides the probability value for a test with predetermined outcomes.

## The Significance of the P-Value in a Binomial Test

The p-value represents the probability value for both the null and alternative hypotheses.