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Two researchers make a test concerning the effects of music on mood. Researcher A tests the effects of rock music on mood and determines that the likelihood of committing a Type II error is = .20; Researcher B tests the effects of classical music on mood and determines that the likelihood of committing a Type II error is = .40. All other things being equal, which researcher has more power to detect an effect? Explain.

7.

The t Table Exercise

Work through the following exercise and write down what you see in the t-table. This will help familiarize you with the table.

The t-table: The degrees of freedom (df) are listed down the far left column. The level of significance for a one-tailed test (top) and two-tailed test (bottom) is listed for each column to the right of the degrees of freedom. So to read the table, you simply need to know the level of significance and degrees of freedom (n –1) for the test.

Increasing the level of significance and degrees of freedom

1. For the following degrees of freedom, list the critical values for a two-tailed test at a .01, .05, and .10 level of significance.

.01 .05 .10

df = 8 ___ ___ ___

df = 20 ___ ___ ___

df = 40 ___ ___ ___

df = 120 ___ ___ ___

2. As the level of significance increases (from .01 to .10), does the critical value increase or decrease?

3. As the degrees of freedom increase (from 8 to 120), does the critical value increase or decrease?

4. How is this related to power? Hint: If you are having trouble, refer to Sections 8.8 and 8.9 in Chapter 8 for a review of factors that influence power.

Comparing the z and the t

5. For the following degrees of freedom, list the critical values for a one-tailed and two-tailed test at a .01 and .05 level of significance.

.01 .05

df = ___ ___ (One-tailed test)

df = ___ ___ (Two-tailed test)

6. Refer to Table 8.4 in Chapter 8. How do the critical values you listed in the previous question compare with those listed for the z-distribution. Explain.

8.

Independent or Dependent Samples Exercise

For each of the following research questions, you will read an independent and dependent samples study to test that research question. Identify which study used independent and which used dependent samples.

1. How does winning influence self-efficacy (or belief in one’s ability) among high school sports athletes?

Study 1: Researchers hypothesized that the more wins a team has, the more teammates will believe in their own abilities (self-efficacy). To test this, they selected a group of sports athletes from teams with few wins during the previous season and a second group of sports athletes from teams with many wins during the previous season. They tested whether self-efficacy significantly differed between groups.

Study 2: Researchers hypothesized that the more wins a team has, the more teammates will believe in their own abilities (self-efficacy). To test this, they measured self-efficacy among athletes during a winning season and again during a losing season the following year. They tested whether the difference in self-efficacy between winning and losing seasons was significantly different.

2. Will levels of the brain chemical dopamine increase in response to food rewards?

Study 1: Researchers hypothesized that dopamine would increase in response to a high-fat food (reward) versus a similar low-fat food. To test this, they presented four adult female Macaca fascicularis monkeys with a high- and low-fat raisin and measured the levels of dopamine in the brain in response to each reward. They tested whether the difference in dopamine levels was significantly different.

Study 2: Researchers hypothesized that the levels of dopamine would increase in response to a larger food reward. To test this, they had animal subjects press a lever to receive a food reward and measured levels of dopamine in the brain in response to this reward. One group received a small food reward and a second group received a large food reward. They tested whether dopamine levels significantly differed between groups.

3. Do English as a second language (ESL) children have the same knowledge of word meanings as English as a first language (ELI) children?

Study 1: Researchers hypothesized that ESL children would have greater difficulty in phonological awareness (the ability to notice, think about, or manipulate the individual sounds in words). To test this, they had one group of ESL children and a second group of ELI children complete a phonological awareness assessment and recorded the scores. They tested whether phonological awareness assessment scores significantly differed between groups.

Study 2: Researchers hypothesized that ESL children would have the same knowledge of word meanings as do their ELI relatives. To test this, they recorded scores on a vocabulary knowledge assessment for ESL children and comparison ELI relatives (of similar ages). They tested whether the difference in vocabulary knowledge assessment scores between these related children was significantly different.

4. How do psychosocial attitudes (those based on the interaction between the individual and the social environment) toward romantic love vary by race/culture?

Study 1: Researchers hypothesized that cultures focused on group identity (collectivist) would place less emphasis on romantic love compared with cultures focused on individual identity (individualistic). To test this, they collected a sample of Chinese (collectivist) and American (individualistic) adolescents and had them complete a romantic love assessment survey. They tested whether scores on this survey significantly differed between groups.

Study 2: Researchers hypothesized that psychosocial attitudes toward love in individualistic cultures would be more negative following the loss of a romantic relationship. To test this, they recorded perceptions of love among a group of American college students during and following a romantic relationship. They tested whether the difference in perceptions of love during and after a romantic relationship was significantly different.

5. Does snacking between meals reduce the number of calories consumed in a meal?

Study 1: Researchers hypothesized that snacking between meals would only reduce calories consumed in the meal if participants thought of the foods as “snack foods” (referred to as cognitive satiety). To test this, on 1 day, they gave a group of participants 100 kcal of a food they thought of as a snack food and recorded the number of calories consumed in the subsequent meal. On the second day, they gave the same group of participants 100 kcal of a food they thought of as a “meal food” and recorded the number of calories consumed in the subsequent meal. They tested whether the difference in calories consumed in the meal from day 1 to day 2 significantly differed.