Chapter 8

r = .10, 95% CI [.05, .15]

statistically significant

When is an outlier most likely to be problematic?

when the sample size is small and the outlier is extreme on both variables

A recent study with 3,000 participants reported a fairly powerful negative correlation between the number of class absences by college students and their GPAs. According to recent guidelines for interpreting the magnitude of effect sizes, what r value was most likely to have been reported in this study?

-.30

Wan notices that more graffiti appears when there are more ice cream trucks in town. She does a study that measures the frequency of new graffiti being reported and ice cream truck sales for each week over a year. She finds a positive association between ice cream truck sales and new graffiti, and she concludes that the ice cream trucks are encouraging graffiti. Her friend, Zizi, points out that both ice cream sales and graffiti might be influenced by rising temperatures during the summer. What kind of problem has Zizi identified?

a third - variable problem

Do college students sleep fewer hours per day than high school students do?

bar graph

Is job title linked to salary?

bar graph

Is type of social media platform associated with feelings of jealously?

bar graph

For her psychology class, Ezra is making a scatterplot of the digit spans (how many numbers you can remember and repeat back), with participants' memory for digits they read on the x-axis and participants' memory for digits they hear on the y-axis. The association is strong, but Ezra notices that one participant has a visual digit memory that is twice as long as anyone else's. What question about statistical validity is Ezra raising?

could outlines be affecting the relationship?

r = .21, 95% CI [−.17, .59]

not statistically significant

r = −.45, 95% CI [−.92, .03]

not statistically significant

What is an essential feature of studies that support association claims?

the studies must involve a correlation between two measured variables

There is a strong positive association between years of education and income. The average income for American adults in 2019 was $48,000 and the average number of years of education was 12. If an individual has 16 years of education, what would you predict about their income?

their income is probably higher than $48,000

Mischel et al. (1972) studied delay of gratification in preschoolers. The researchers offered preschoolers a special reward if they could wait, or a less attractive treat if they chose not to wait. The researchers then conducted a follow-up study years later, studying the same preschoolers as adolescents. The researchers found a positive association between the preschoolers' waiting times and their self-control as adolescents. Match each question to the type of validity it interrogates.

Can the results be generalized to all American children?external validity How well was delay of gratification measured?construct validity Has this association been replicated?statistical validity statistical validity Is there a third variable that explains this relationship? internal validity

Siva is investigating an association claim between political beliefs and age. His data show a correlation of r = .35. However, upon closer examination, Siva finds that the correlation is much stronger for men than it is for women. What type of variable is gender is this example?

Moderator

Sahil wants to investigate the relationship between reaction time and experience in tennis. He is considering different ways to operationalize tennis experience in his claim. Match each type of graph or data analysis method to the correct association claim.

Reaction times decrease as the number of years playing tennis increases. scatterplot & correlation Coefficient r Reaction times are shorter in tennis experts than in nonexperts. magnitude of difference between means & bar graph

The Yerkes-Dodson law (1908) shows that performance increases with arousal up to a point, but beyond that, performance decreases as arousal increases. Which type of association is this?

curvilinear

Is length of experience linked to salary?

scatterplot

Is time spent using social media associated with feelings of jealously?

scatterplot

r = −.23, 95% CI [−.33, −.13]

statistically significant

José is investigating the relationship between exam anxiety and exam grades. He collects students' ratings of their own anxiety before an exam, and then he collects their exam scores afterward. When he calculates the correlation, he finds no relationship. José plots his data on this scatterplot and sees that both students who had no anxiety and students who had lots of anxiety performed poorly on exams—but students who reported moderate anxiety did very well. What issue is most likely affecting José's results?

curvilinear association

Chenoa finds a positive association between hours of sleep and well-being, and she wants to see whether this association is the same for teenagers (ages 16-19) as it is for young adults (ages 20-24). What discovery would suggest that the association between hours of sleep and well-being is a spurious association?

overall teenagers report sleeping more and having greater well-being than young adults

Professor Schwartz is examining the relationship between time spent at a shopping mall and happiness. She finds that for millennials, more mall time is associated with higher levels of happiness, but for baby boomers, more mall time is associated with lower levels of happiness. What is the moderator in this relationship?

generation

Francisco is conducting an international study about a new website that is preparing to launch worldwide. He wants to see whether men or women are more likely to be interested in the new website so he can know which demographic to market it to. After he collects his data, Francisco discovers that whether the men and women surveyed were from Asia or North America changed how they responded to the website. Men from Asian countries were the most interested in his website, whereas women from North American countries were the least interested. Match each variable in Francisco's study to the correct definition.

moderator - Geographic area dependent variable - interest indecent variable - gender

Vanessa is investigating the relationship between socioeconomic status and mental illness. She samples a group of low-income participants and finds that the relationship between her two variables is very weak. Vanessa plots her data on this scatterplot and does not see any obvious problems with it. What issue is most likely affecting Vanessa's results?

restriction of range

Is age associated with number of hours of sleep?

scatterplot