Hypothesis Testing Overview
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Questions and Answers

What is the definition of the alternative hypothesis?

  • It claims that the parameter has a value differing from the null hypothesis. (correct)
  • It states that the parameter is equal to a specific value.
  • It represents the initial assumption before testing.
  • It is always stated after rejecting the null hypothesis.

Which of the following symbols can be used in the alternative hypothesis?

  • (correct)
  • >=
  • <=
  • ==

What is the correct form of the null hypothesis when testing if the mean weight is at most 195 lb?

  • H0: µ < 195 lb
  • H0: µ > 195 lb
  • H0: µ = 195 lb (correct)
  • H0: µ ≤ 195 lb

What conclusion can be drawn if the null hypothesis is rejected?

<p>The alternative hypothesis is accepted. (C)</p> Signup and view all the answers

What does the critical region represent in hypothesis testing?

<p>Values that lead to rejecting the null hypothesis. (D)</p> Signup and view all the answers

In a hypothesis test, what does failing to reject H0 imply?

<p>Data does not provide sufficient evidence to favor H1. (A)</p> Signup and view all the answers

Which statement is true regarding the symbols used in hypotheses?

<p>H0 typically includes an equal sign. (A)</p> Signup and view all the answers

When should the null and alternative hypotheses be stated?

<p>Before conducting any statistical test of significance. (D)</p> Signup and view all the answers

What type of hypothesis test is used when testing if a mean has either increased or decreased?

<p>Two-tailed test (A)</p> Signup and view all the answers

In a right-tailed hypothesis test, where is the significance level α placed?

<p>In the right tail only (B)</p> Signup and view all the answers

What are the null and alternative hypotheses in the given example about backpack weights?

<p>H0: µ = 8.4 kg and H1: µ ≠ 8.4 kg (D)</p> Signup and view all the answers

Which of the following statements is true about a left-tailed test?

<p>It tests for a decrease in the mean only. (B)</p> Signup and view all the answers

What does the symbol H0 signify in hypothesis testing?

<p>Null hypothesis (C)</p> Signup and view all the answers

If a hypothesis test is two-tailed, how is the α divided?

<p>Equally between both tails (D)</p> Signup and view all the answers

In hypothesis testing, what does the alternative hypothesis (H1) indicate?

<p>The mean is not equal to a specified value. (C)</p> Signup and view all the answers

Which hypothesis test would you use to test if the average weight of backpacks has decreased since a given mean?

<p>Left-tailed test (A)</p> Signup and view all the answers

What is the value of the test statistic z in the hypothesis test?

<p>1.52 (D)</p> Signup and view all the answers

What is the corresponding critical value z for α = 0.05?

<p>1.65 (B)</p> Signup and view all the answers

What conclusion is made when the test statistic does not fall in the critical region?

<p>Fail to reject H0 (C)</p> Signup and view all the answers

What is the margin of error calculated using the z value and sample size?

<p>6.783 (C)</p> Signup and view all the answers

What does the P-value of 0.0643 indicate about the sample mean of 172.55 lb?

<p>It could happen by chance. (B)</p> Signup and view all the answers

What is the 90% confidence interval constructed from the sample mean and margin of error?

<p>(165.8, 179.3) (A)</p> Signup and view all the answers

What is the population mean assumption in this hypothesis test?

<p>166.3 lb (D)</p> Signup and view all the answers

What method is used to test the claim about the population mean in the example?

<p>Traditional method (B)</p> Signup and view all the answers

What does a P-value of 0.0014 indicate if the significance level is α = 0.01?

<p>Reject the null hypothesis (A)</p> Signup and view all the answers

Which condition is necessary when testing a claim about a mean with an unknown standard deviation?

<p>The sample must be a simple random sample (C)</p> Signup and view all the answers

What is the formula to find degrees of freedom when testing a claim about a mean?

<p>df = n - 1 (A)</p> Signup and view all the answers

What does the Student t distribution reflect about variability?

<p>It reflects greater variability compared to the normal distribution (B)</p> Signup and view all the answers

As the sample size increases, what happens to the Student t distribution?

<p>It approaches the standard normal distribution (D)</p> Signup and view all the answers

What is the mean of the Student t distribution?

<p>t = 0 (A)</p> Signup and view all the answers

What is a requirement for the population when testing claims about a mean?

<p>Population is normally distributed or sample size n &gt; 30 (B)</p> Signup and view all the answers

What is a characteristic of the Student t distribution for different sample sizes?

<p>It differs based on the sample size (B)</p> Signup and view all the answers

What is a Type I error in hypothesis testing?

<p>Rejecting the null hypothesis when it is actually true. (B)</p> Signup and view all the answers

What symbol represents the probability of a Type I error?

<p>α (A)</p> Signup and view all the answers

Which step involves stating the original claim in symbolic form?

<p>Identify the specific claims. (A)</p> Signup and view all the answers

What do you do if the P-value is greater than α?

<p>Fail to reject H0. (B)</p> Signup and view all the answers

When should you select a smaller significance level α?

<p>When the consequences of rejecting a true H0 are severe. (D)</p> Signup and view all the answers

In hypothesis testing, a Type II error is defined as:

<p>Failing to reject the null hypothesis when it is false. (A)</p> Signup and view all the answers

What is the first step in the P-value method?

<p>Identify the specific claims. (A)</p> Signup and view all the answers

What must be true when the original claim is false?

<p>The alternative hypothesis represents the true situation. (C)</p> Signup and view all the answers

What type of test is used when the alternative hypothesis suggests the mean is less than a specified value?

<p>Left-tailed test (C)</p> Signup and view all the answers

Given the null hypothesis $H_0 : µ = 12$ ounces, what is the alternative hypothesis for this scenario?

<p>$H_1 : µ &lt; 12$ ounces (C)</p> Signup and view all the answers

How is the P-value interpreted in hypothesis testing?

<p>It represents the probability of obtaining the observed data if the null hypothesis is true. (C)</p> Signup and view all the answers

What happens if the P-value is less than 0.05 in hypothesis testing?

<p>The null hypothesis is rejected. (B)</p> Signup and view all the answers

In the context of hypothesis testing, what is the critical region?

<p>The range of values where the null hypothesis is rejected. (D)</p> Signup and view all the answers

For a left-tailed test, how is the P-value determined?

<p>By calculating the area to the left of the test statistic. (D)</p> Signup and view all the answers

Which hypothesis test would involve a P-value calculated as twice the area in the tail beyond the test statistic?

<p>Two-tailed test (B)</p> Signup and view all the answers

What identifies a left-tailed test in the hypothesis testing framework?

<p>The alternative hypothesis specifies a less than condition. (B)</p> Signup and view all the answers

Flashcards

Alternative Hypothesis (H1)

The statement that the parameter has a value that differs from the null hypothesis. It involves symbols like ≠, >, or < to describe the difference.

Null Hypothesis (H0)

The assumed statement about a population parameter (like proportion, mean, or standard deviation). It's assumed to be true initially, and then evidence is gathered to either reject or fail to reject it.

Critical Region

The set of values of the test statistic that lead us to reject the null hypothesis. If the calculated test statistic falls within this region, you reject the null hypothesis.

Hypothesis Testing Process

In hypothesis testing, we typically assume the null hypothesis is true and gather evidence to see if it's likely false. If the evidence strongly suggests the null hypothesis is false, we reject it. If not, we fail to reject it.

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Significance Level (α)

It's a value that determines how strong the evidence must be to reject the null hypothesis. A lower significance level means stronger evidence is required.

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Decision Rule

The process of deciding whether to reject or fail to reject the null hypothesis based on the collected data and calculated test statistic.

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P-value

It represents the probability of making a Type I error – rejecting the null hypothesis when it's actually true.

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Testing a Claim About a Proportion

It's a statistical test in which the objective is to determine if there is statistically significant evidence to reject a claim about a population proportion (e.g., the percentage of voters supporting a candidate).

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Hypothesis Test

A statistical test used to determine whether a population parameter is different from a hypothesized value.

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Two-tailed Hypothesis Test

A hypothesis test where the alternative hypothesis states that the population parameter is not equal to a specific value.

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Left-tailed Hypothesis Test

A hypothesis test where the alternative hypothesis states that the population parameter is less than a specific value.

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Right-tailed Hypothesis Test

A hypothesis test where the alternative hypothesis states that the population parameter is greater than a specific value.

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Test for a Proportion

A hypothesis test used to determine whether the proportion of a population with a certain characteristic is different from a hypothesized value.

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Test for Mean (σ Known)

A hypothesis test used to determine whether the mean of a population is different from a hypothesized value when the population standard deviation is known.

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Testing a Claim About a Mean

A statistical test where you aim to determine if a claim about a population mean is true based on a sample.

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Two-tailed Test

The type of hypothesis test where you're interested in whether the parameter is significantly different from a specific value.

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Left-tailed Test

The type of hypothesis test where you're interested in whether the parameter is significantly lower than a specific value.

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Right-tailed Test

The type of hypothesis test where you're interested in whether the parameter is significantly higher than a specific value.

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Type I Error

The probability of rejecting the null hypothesis when it is actually true.

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Type II Error

The probability of failing to reject the null hypothesis when it is actually false.

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t-Distribution

The Student t-distribution is used when the population standard deviation (σ) is unknown. It accounts for the additional uncertainty introduced by estimating σ from the sample.

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Degrees of Freedom (df)

The Student t-distribution is a family of distributions indexed by degrees of freedom (df). As df increases, the t-distribution approaches the standard normal distribution.

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Shape of the t-Distribution

The t-distribution has a wider shape than the normal distribution, reflecting the increased variability when estimating σ from the sample.

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Mean of the t-Distribution

The t-distribution has a mean of 0, just like the standard normal distribution.

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Standard Deviation of the t-Distribution

The standard deviation of the t-distribution depends on the sample size; larger samples lead to a smaller standard deviation.

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t-Distribution and Large Sample Size

When the sample size (n) is large (often considered n > 30), the t-distribution closely resembles the standard normal distribution. This allows us to use z-tables for large samples.

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Hypothesis Testing with the t-Distribution

The t-distribution is used in hypothesis testing for population means when the population standard deviation (σ) is unknown. This is often the case in real-world situations.

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Normality Assumption for Small Samples

When the sample size is less than 30, the population should be approximately normally distributed to use the t-distribution.

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Study Notes

Hypothesis Testing Overview

  • Hypothesis testing is a procedure used to test claims about a population parameter.
  • Population parameters are often estimated, but hypotheses can be formed.

Hypothesis and Hypothesis Test

  • A hypothesis is a claim or statement about a population property.
  • A hypothesis test is used to test a claim about a population property.

Null Hypothesis (H₀)

  • The null hypothesis is the hypothesis to be tested.
  • It's often denoted as H₀.
  • Typically states that a population parameter (e.g., proportion, mean, standard deviation) is equal to a specific value.
  • It is assumed to be true initially.
  • The conclusion is either to reject or fail to reject the null hypothesis.

Alternative Hypothesis (H₁)

  • The alternative hypothesis (denoted by H₁, Hₐ, or Hₐ) represents the opposite of the null hypothesis.
  • It suggests that the parameter's value differs from the null hypothesis in some way (≠, <, or >).
  • The symbolic alternative hypothesis must contain one of these signs: ≠, <, >

Stating H₀ and H₁

  • The null hypothesis is usually stated with an equal sign (=).
  • The alternative hypothesis is stated without an equal sign (≠, <, or >).
  • The true value of the population parameter should be included in a set specified by H₀ or in a set specified by H₁.

Critical Region and Significance Level (α)

  • The critical region is the set of all test statistic values that lead to rejecting the null hypothesis.
  • The significance level (α) is the probability of rejecting the null hypothesis when it's actually true (making the mistake of rejecting the null when it's true).
    • Common values for α include 0.05, 0.01, and 0.10.

Test Statistic

  • The test statistic is a value used to make decisions about the null hypothesis. It's derived by converting a sample statistic to a score assuming the null hypothesis is true.
    • Different formulas for different scenarios (mean, proportion).

Critical Value

  • A critical value separates the critical region from the values of the test statistic that do not lead to rejection.
  • The critical values depend on the null hypothesis, the sampling distribution, and the significance level (α).

Types of Hypothesis Tests

  • Two-tailed: critical region is in both tails of the distribution.
  • Left-tailed: critical region is in the left tail.
  • Right-tailed: critical region is in the right tail.

P-value

  • The probability of obtaining a test statistic as extreme or more extreme than the one representing the sample data, assuming the null hypothesis is true.
  • If the p-value is very small (e.g., less than 0.05), the null hypothesis is often rejected.

Decisions and Conclusions

  • Do not use "Accept" for "Fail to Reject."
  • Avoid multiple negatives in the conclusion.

Errors in Hypothesis Tests

  • Type I Error: Rejecting the null hypothesis when it's true (probability denoted by α).
  • Type II Error: Failing to reject the null hypothesis when it's false (probability denoted by β).

Confidence Method

  • Constructing a confidence interval to test a claim about a population parameter.
  • A claim is rejected if the population parameter value is not included in the confidence interval.

Testing a Claim About a Mean (σ Known)

  • Methods for testing claims about a population mean when the population standard deviation is known.
  • Requirements: a simple random sample, known population standard deviation, and a normally distributed population or a large enough sample size (n ≥ 30).

Testing a Claim About a Mean (σ Not Known)

  • Methods for testing claims about a population mean when the population standard deviation is not known.
  • Requirements: a simple random sample, unknown population standard deviation, and a normally distributed population or large enough sample size (n ≥ 30).

Important Properties of the Student t Distribution

  • It differs depending on the sample size.
  • It has the same shape as a normal distribution but is wider, reflecting that sample standard deviation has more variability than population standard deviation.
  • It has a mean of zero.
  • Its standard deviation varies with sample size.
  • As the sample size increases, it approaches the standard normal distribution.

Finding P-Values with the Student t Distribution

  • Determining a range of p-values using the t-table, not exact values.
  • Locate the relevant row of the t-table using degrees of freedom.
  • Determine where the test statistic falls relative to the t-values in that row.
  • Estimate the area using area values in the t-table to get the range of the p-value.

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Ch. 9 - Hypothesis Testing PDF

Description

This quiz covers the essential concepts of hypothesis testing, including the definitions and roles of null and alternative hypotheses. Understand how to formulate claims regarding population parameters and the importance of hypothesis testing in statistical analysis.

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