PSY230 Practice Problems Lesson 8 Hypothesis Testing
Which of the following changes will increase the power of a statistics test:
Change sample size from 20 participants to 80 participants Power is increased when a researcher increases sample size, as well as when a researcher increases effect sizes and significance levels
The critical boundary for a hypothesis test was ± 1.96. The z-score was - 1.90. What should the researcher do:
Fail to reject H0 - null hypothesis
A public health researcher wants to know whether a new tax that was placed on soda has had any impact on people's behavior. Before the new tax, convenience stores in the city sold an average of µ = 410, sugar filled beverages per day with σ = 60. The distribution was normal. Following the new tax, data were collected for a sample of n = 9 days and the new mean was M = 380 from the same convenience stores. Using a two-tailed test with .05 level of significance and a z-score of -1.50 can the researcher conclude that there was a statistically significant change in behavior.
No fail to reject the null hypothesis
The null hypothesis states:
The population mean after treatment is the same as it was before treatment
Which combination of factors will increase the chances of rejecting the null hypothesis:
a small standard error and a large alpha level
Critical boundaries are set by:
alpha level
A cultural psychologist was interested in differences in personality across several small scales subsistence cultures and records the results. If the researcher makes a Type II error it means that he researcher has ______.
concluded that a treatment has no effect when it really does A type II error produces a false negative, also known as an error of omission. For example, a test for a disease may report a negative result, when the patient is, in fact, infected. This is a type II error because we accept the conclusion of the test as negative even though it is incorrect. type II error describes the error that occurs when one fails to reject a null hypothesis that is actually false. The error rejects the alternative hypothesis, even though it does not occur due to chance.
Even if a treatment has no effect it is still possible to obtain an extreme sample mean that is very different from the population mean. If this happens, you are likely to ____
reject H0 and make a Type I error.
A psychologist is examining compliance and marketing using a series of advertisements. She records her results. If the researcher makes a Type 1 error she has concluded that:
the sample is different from the population but it is not
A psychologist is examining compliance and marketing using a series of advertisements. She records the results. If the researcher makes a Type 1 error she has concluded that:
the sample is different from the population but it is not. type I error rejects the null hypothesis when it is true (i.e. a false positive). The probability of committing a type I error is equal to the level of significance that was set for the hypothesis test. Therefore, if the level of significance is 0.05, there is a 5% chance a type I error may occur.
