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One-Tailed Test
A one-tailed test is a hypothesis test in which the null hypothesis is rejected only if the test statistic is extreme in one specific direction, which must be hypothesized prior to data collection. By utilizing only a single critical value, this test increases the likelihood of finding a statistically significant result if the data trends in the expected direction, but completely eliminates the possibility of rejecting the null hypothesis if the results go in the opposite direction.
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Research Methods in Psychology - 4th American Edition @ KPU
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One-Tailed Test
Example of a Two-Tailed Test
A researcher is exploring whether a new background noise level changes the time it takes for participants to complete a puzzle. Because they are unsure if the noise will make participants faster or slower, they choose to use a Two-Tailed Test. Based on this choice, when will the researcher reject the null hypothesis?
A clinical psychologist is conducting a study to see if a new mindfulness exercise changes the average number of hours patients sleep per night. They expect a difference but do not know if sleep will increase or decrease, so they opt for a two-tailed test. Arrange the following steps of their hypothesis testing process in the correct chronological order.
A psychology researcher is analyzing the effects of a new therapy on anxiety scores using a two-tailed test. Match each statistical component with the description that accurately analyzes its functional role in the structure of this non-directional hypothesis test.
A psychologist evaluating the efficacy of a new antidepressant uses a two-tailed test. Although they expect the drug to reduce symptoms, they justify the two-tailed approach as being more scientifically rigorous because it allows for the statistical detection of an unexpected increase in symptoms. This justification is methodologically sound because, at a fixed significance level of , the two-tailed test requires a more extreme result to justify rejecting the null hypothesis in the predicted direction than a test that only considers a single tail of the distribution.
In the context of hypothesis testing, how many distinct critical values are typically utilized to establish the rejection regions for a two-tailed test?
A researcher should only use a two-tailed test if they have a strong theoretical justification for predicting that the experimental results will be significantly higher than the hypothesized population mean.
An approach to hypothesis testing where researchers reject the null hypothesis if their calculated test statistic falls into the extreme regions of either the positive or negative tail of the distribution is called a _____ test.
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Example of a One-Tailed Test
Which of the following best describes when the null hypothesis is rejected in a one-tailed test?
If a researcher conducts a one-tailed test predicting that a new study technique will increase exam scores, but the results show a statistically significant decrease in scores, the researcher must fail to reject the null hypothesis.
A psychologist is conducting various studies using a one-tailed hypothesis test. Match each research scenario with the appropriate statistical decision and the rationale for that choice.
Arrange the following steps to reflect the logical process and the specific constraints involved when a researcher correctly applies a one-tailed hypothesis test in psychological research.
A psychologist predicts that a new mindfulness app will decrease stress levels and decides to use a one-tailed test. What is the primary statistical advantage of this decision compared to using a test that looks for a change in either direction?
A clinical researcher utilizes a one-tailed test () to evaluate the hypothesis that a new medication will decrease heart rate. If the medication unexpectedly causes a statistically extreme increase in heart rate, the researcher is forced to fail to reject the null hypothesis. From an evaluative standpoint, this demonstrates that the one-tailed test is inherently biased because it treats any result in the unpredicted direction as statistically _____ to a result showing no change.
A one-tailed test increases the likelihood of finding a statistically significant result in the predicted direction by utilizing a(n) _____ critical value.
A cognitive psychologist hypothesizes before data collection that a new memory training program will increase recall scores, and decides to use a one-tailed test. After compiling the data, the results show that participants in the training program actually had an extremely large, statistically significant decrease in recall scores. True or False: Under the rules of this one-tailed test, the psychologist can reject the null hypothesis because the result was highly extreme.
A researcher is planning a study to test whether a new focus app increases study time, using a one-tailed test. Match each research design component with its correct outcome or requirement based on the properties of a one-tailed test.
A developmental psychologist wants to evaluate and apply a one-tailed hypothesis test to determine if a new educational game increases spatial reasoning skills. Order the steps of this research evaluation process from the initial design phase to the final statistical decision.
Define a one-tailed test based on when the null hypothesis is rejected, and describe its primary advantage and disadvantage in statistical testing.
Based on the properties of the chosen statistical test, what must the researcher decide regarding the null hypothesis, and why? Explain this outcome in terms of the test's critical value.
A clinical researcher believes a new cognitive therapy will decrease intrusive thoughts in patients. The researcher wants to maximize the statistical chance of detecting this specific improvement if the therapy works. What specific type of hypothesis test should they apply before collecting data, and what structural feature of this test achieves their goal?