Quiz 10 - Chapter 10: Independent-Samples t-Test Flashcards
A researcher conducted an independent samples t-test to see if there was a difference between first-year college students and fourth-year college students in terms of the number of hours they sleep per night. The researcher sampled 45 first-year students and had 80 degrees of freedom for the independent samples t-test they ran. How many fourth-year students did they sample?
37
N1 + N2 - 2 = Degrees of Freedom
A drug company wants to see if a new antidepressant reduces depression levels among U.S. adults. If the company wants to use an independent samples t-test to test this, how should they sample participants and administer treatment in their study?
A: They should randomly assign sampled U.S. adults to take either the new antidepressant or a placebo, and then measure the depression levels of the adults in both groups. They should then compare the depression levels of the adults in the treatment group to the depression levels of the adults in the placebo group to see if there is a significant difference.
B: They should sample a single group of U.S. adults, measure their depression levels before they take the drug, measure their depression levels after they take the drug, and then compare the pre-and post-depression levels to see if there is a significant difference between them.
A: They should randomly assign sampled U.S. adults to take either the new antidepressant or a placebo, and then measure the depression levels of the adults in both groups. They should then compare the depression levels of the adults in the treatment group to the depression levels of the adults in the placebo group to see if there is a significant difference.
Which of the following research scenarios would require an independent samples t-test?
A: Husband and wife pairs are compared to see which gender reports the highest level of marital satisfaction
B: Students in a social psychology experiment read a pair of vignettes, then they rate the friendliness of two faces that differ in their ethnicity
C: Pretest and posttest scores are obtained from a group of people prior to and after they participate in a smoking cessation intervention
D: To examine test bias, an educational researcher compares test scores between males and females
D: To examine test bias, an educational researcher compares test scores between males and females
A researcher is interested in understanding the effect of mindfulness on undergraduate students and graduate students. If the researcher found that there’s a non-significant difference between the effects of mindfulness on undergraduate students and graduate students, what can you conclude?
A: We are sure that there’s no difference between the effects of mindfulness on undergraduate students and graduate students
B: It is plausible that there’s no difference between the effects of mindfulness on undergraduate students and graduate students
C: There is a difference between the effects of mindfulness on undergraduate students and graduate students
B: It is plausible that there’s no difference between the effects of mindfulness on undergraduate students and graduate students
A psychologist is interested in determining whether a new treatment for depression impacts depression scores. She randomly assigns 25 subjects to the treatment and 31 subjects to the control. She uses an independent samples t-test to evaluate whether the groups differ, subtracting the control group mean from the treatment group mean. The t-statistic is -2.70 with a probability value (p-value) of .009 (a two-tailed test). Which of the following conclusions is true regarding the treatment? Check all that apply.
A: Results are inconclusive; the intervention may or may not have worked
B: The treatment impacts depression scores in a matter that is consistent with random chance (sampling error)
C: If there is really no difference between treatment and control groups in the population, the probability of drawing a sample with a t statistic of ± 2.70 or more extreme is .009
D: The treatment group improves scores compared to the control group beyond what is expected due to random chance (sampling error)
C: If there is really no difference between treatment and control groups in the population, the probability of drawing a sample with a t statistic of ± 2.70 or more extreme is .009
D: The treatment group improves scores compared to the control group beyond what is expected due to random chance (sampling error)
A researcher studies whether there is any difference between males and females in time spent playing mobile games. She recruits 30 females and 32 males, and records the number of hours they spend playing mobile games per week. She reports that the standardized mean difference effect size between the female and male groups is 0.12 (the group mean of male is higher than that of female). Which of the following statements is correct?
A: The male group mean is 0.12 hours higher than the female group mean
B: The male group mean is 0.12 minutes higher than the female group mean
C: The mean difference between the female and male groups is about 12% the size of what we would expect due to sampling error alone
D: Relative to the female group, the male group mean is 12% higher
E: The mean difference between the female and male groups is equivalent to about 0.12 standard deviation units
F: The mean difference between the female and male groups is about 0.12 times as large as the standard error
E: The mean difference between the female and male groups is equivalent to about 0.12 standard deviation units
> This is Cohen’s d
A researcher studies the difference in time spent playing mobile games between males and females. She recruits 56 females and 50 males, and records the number of hours they spend playing mobile games per week. She finds that the standard error of the group mean difference is 1.1. Which of the following statements is correct? Check all that apply.
A: The average difference between an individual score and the true population mean difference is 1.1 hours.
B: The average difference between an individual score in group 1 and the true population mean of group 1 is 1.1 hours.
C: If there are many studies with the same sample sizes, the standard deviation of the sample mean differences from these studies will be 1.1 hours.
D: The average difference between the sample mean difference and the true population mean difference is 1.1 hours.
E: The average difference between an individual score and the sample population mean difference is 1.1 hours.
F: If there are many studies with the same sample sizes, we can make a sampling distribution of these mean differences. The standard deviation of this sampling distribution will be 1.1 hours.
C: If there are many studies with the same sample sizes, the standard deviation of the sample mean differences from these studies will be 1.1 hours.
D: The average difference between the sample mean difference and the true population mean difference is 1.1 hours.
F: If there are many studies with the same sample sizes, we can make a sampling distribution of these mean differences. The standard deviation of this sampling distribution will be 1.1 hours.
A researcher studies the differences in time spent playing mobile games between males and females. She recruits 56 females and 50 males, and records the number of hours they spend playing mobile games per week. She reports that the t statistic is 2.5 (the group mean of male is higher than that of female). Which of the following statements is correct? Check all that apply.
A: The male group mean is 2.5 times as large as the female group mean
B: The mean difference between the female and male groups is about 2.5 times as large as the standard error
C: The mean difference between the female and male groups is equivalent to about 2.5 standard deviation units
D: The mean difference between the female and male groups is about 2.5 times as large as what we would expect due to sampling error alone
E: Relative to the female group, the male group mean is 2.5 times higher
F: The mean difference between the female and male groups is equivalent to about 2.5 times the average standard deviation
B: The mean difference between the female and male groups is about 2.5 times as large as the standard error
D: The mean difference between the female and male groups is about 2.5 times as large as what we would expect due to sampling error alone
A researcher studies the differences in time spent playing a mobile game called Pokemon GO between males and females. She recruits 50 females and 50 males, and records the number of hours they spend playing this mobile game per week. She finds that the confidence interval includes 0. Which of the following statements is correct?
A: There is no significant difference between females and males in the time spent playing Pokémon GO
B: Results are inconclusive; we have to make the conclusion based on the t statistic and the p-value
C: There is a significant difference between females and males in the time spent playing Pokémon GO
A: There is no significant difference between females and males in the time spent playing Pokémon GO
A researcher decides to conduct an independent samples t-test to see whether a new drug lowers anxiety significantly more than a placebo (the null hypothesis is that the group means are equal). They randomly assign participants to either a treatment group or a control group, give participants the appropriate treatment (i.e., either the new drug or the placebo), and then measure the participants’ anxiety levels. The researcher finds the mean anxiety level in the treatment group to be 4.8 and the mean anxiety level in the control group to be 5.2. If the Cohen’s d effect size for their study was .26, how was the mean difference calculated?
A: The treatment group mean was subtracted from the control group mean, and then the difference was divided by the average standard deviation
B: The control group mean was subtracted from the treatment group mean, and then the difference was divided by the average standard deviation
C: We cannot decide based on the information given
A: The treatment group mean was subtracted from the control group mean, and then the difference was divided by the average standard deviation
A researcher decides to conduct an independent samples t-test to see whether a new drug lowers anxiety significantly more than a placebo (the null hypothesis is that the group means are equal). They randomly assign participants to either a treatment group or a control group, give participants the appropriate treatment (i.e., either the new drug or the placebo), and then measure the participants’ anxiety levels. The researcher finds the mean anxiety level in the treatment group to be 4.8 and the mean in the control group to be 5.2. If the researcher subtracts 4.8 from 5.2 and then divides this difference by the standard error of the treatment group mean to calculate their t statistic, what if anything have they done incorrectly?
A: They have not done anything incorrectly
B: They should divide by the average standard deviation instead
C: They should divide by the standard deviation of the treatment group instead
D: They should divide by the standard error of the mean difference instead
E: They should subtract 5.2 from 4.8 instead
D: They should divide by the standard error of the mean difference instead
A developmental psychologist wants to know how many words children learn at age of 3 years and age of 4 years. They don’t have the resources to collect data longitudinally so they get two samples: 50 3-year-olds and 50 4-year-olds. They measure the vocabulary size of each group and run an independent-samples t-test. What possible alternative hypotheses could they have? Check all that apply.
A: 3-year-olds and 4-year-olds know the same amount of words
B: 4-year-olds know more words than 3-year-olds
C: 4-year-olds and 3-year-olds know a different amount of words
B: 4-year-olds know more words than 3-year-olds
C: 4-year-olds and 3-year-olds know a different amount of words
A researcher recruits 100 undergraduate students and randomly assigns 50 students to eat chicken and 50 students to eat fish. After eating, each student runs 1 mile and their time is recorded (in minutes). To calculate the group mean difference, the researcher subtracts the average chicken-eater mile from the average fish-eater mile. She runs a two-tailed independent samples t-test and calculates a 95% confidence interval of [-0.37,-0.07]. Which of the following is a correct interpretation of the 95% confidence interval?
A: We are 95% confident that the population mean difference mile time between chicken eaters and fish eaters is between -0.37 and -0.07.
B: We are 95% confident that the sample mean difference mile time between chicken eaters and fish eaters is between -0.37 and -0.07.
C: We are 95% confident that the next time the researcher runs this study, the mean difference mile time between chicken eaters and fish eaters will be between -0.37 and -0.07.
A: We are 95% confident that the population mean difference mile time between chicken eaters and fish eaters is between -0.37 and -0.07.
A researcher randomly assigns participants to one of two groups: anxiety medication or placebo. She has a one-sided alternative hypothesis that the anxiety medication group will have lower anxiety scores than the placebo group. If the anxiety medication group has an anxiety score of 6.1, which of the following placebo group scores would most likely result in a statistically significant finding?
A: 6.1
B: 7.0
C: 5.9
B: 7.0
