Chapter 8 Research Methods

There is a strong positive association between years of education and income. The mean income for American adults in 2005 was $32,000 and the average number of years of education was 12. If Mr. Lopez has 16 years of education, which would you predict about his income?

His income is probably higher than $32,000.

Professor Fofana wonders if there is an association between students' grades and extra credit points earned in his classes. He makes a scatterplot, with the number of extra credit points earned on the x-axis and the numerical grade in his course without extra credit on the y-axis. He finds r = .28 and p < .001. Which of the following correctly explains what this means?

It is very unlikely this association was found in the sample when, in the full population, there is really no association.

In addition to effect size, you must also know which of the following to determine if a correlation is statistically significant?

sample size

Mischel (1972) studied delay of gratification in preschoolers: Children were offered a special reward if they could wait or a less attractive treat if they chose not to wait. A follow-up study was done years later, looking at the same children as adolescents. The researchers found an association between the waiting times of the preschoolers and parents' reports of the same children's behaviors as adolescents. Overall, a positive relationship between waiting time as a preschooler and self-control in adolescence emerged. Which correctly answers whether a causal relationship can be inferred?

No, because internal validity was not established.

Professor Fofana wonders if there is an association between students' grades and extra credit points earned in his classes. He makes a scatterplot, with the number of extra credit points earned on the x-axis and the numerical grade in his course without extra credit on the y-axis. He finds r = .28. What does this correlation tell him about which students take advantage of the extra credit option?

Students with higher grades are more likely than students with lower grades to do extra credit work.

Dr. Stevens wants to examine the relationship between body mass index (BMI) and depression. He selects as his research subjects a sample of American athletes who are currently training for the summer Olympic Games. Dr. Stevens finds no relationship between BMI and depression. Which of the following is one problem with his research design that could have kept him from finding a relationship between those variables?

There is a restriction-of-range problem.

Which of the following is an essential feature of studies that support association claims?

They involve two measured variables.

If the relationship between two variables changes depending on the level of another variable c, which of the following is the term for this other variable, c?

a moderator

Jenna is interested in the association between the height of professional basketball players and their free-throw shooting percentage. She looks at the correlation between NBA players and their free-throw percentage from last season and she finds a statistically significant negative association. Jenna's friend Elizabeth suggests Jenna should look at a scatterplot of the data. Jenna follows Elizabeth's advice and finds one of the players is much shorter than the rest of the players and that player has a much better free-throw shooting percentage. When Jenna removes this player from her analysis, she finds there is no longer a statistically significant relationship between height and free-throw shooting. Which kind of problem has Elizabeth helped Jenna identify?

a problem with an outlier in the sample

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

curvilinear

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

generation of the people being examined

Vida is studying the connection between school grades and time spent using social media. She measures social media use at the beginning of the semester and grades at the end of the semester. Vida finds using more social media early in the semester was linked with lower school grades. Which other criterion of causality does she need if she wants to establish causation?

internal validity

Which type of validity is important to interrogate for causal claims, but not association claims?

internal validity

Researchers de Abreu, Gathercole, and Martin (2011) found the correlation of nonword repetition and digit recall in a memory was r = .59. Based on Cohen's (1992) guidelines, which of the following describes this effect size?

large

Professor Fofana wonders if there is an association between students' grades and whether they complete extra credit in his classes. He makes a scatterplot, with the number of extra credit points earned on the x-axis and the numerical grade in his course without extra credit on the y-axis. He finds r = .28. According to Cohen's conventions, how strong is this association?

medium, or moderate

Mischel (1972) studied delay of gratification in preschoolers: Children were offered a special reward if they could wait or a less attractive treat if they chose not to wait. A follow-up study was done years later, looking at the same children as adolescents. The researchers found an association between the waiting times of the preschoolers and parents' reports of the same children's behaviors as adolescents. The parents' ratings of likelihood of yielding to temptation correlated with the preschool waiting time measurement at r = −.50. Which describes this effect size according to Cohen's benchmarks?

strong

To look at the relationship between reaction time and level of expertise in tennis, experts and nonexperts in tennis were compared. Which of the following would be the most appropriate, easiest way to evaluate the relationship between these variables?

t test and a bar graph

Professor Fofana wonders if there is an association between students' grades and extra credit points earned in his classes. He makes a scatterplot, with the number of extra credit points earned on the x-axis and the numerical grade in his course without extra credit on the y-axis. He finds r = .28. In addition to this correlation coefficient, which of the following would Professor Fofana need to determine if this result is statistically significant?

the sample size

When is an outlier most likely to be problematic?

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

Michelle found a positive association between hours of sleeping and well-being. She looked to see whether this association was the same for teenagers (ages 16-19) and young adults (ages 20-24). Which of the following would most likely suggest this association between hours of sleep and well-being is a spurious association?

Hours of sleep and well-being are positively associated because, overall, teenagers report sleeping more and having greater well-being than young adults.

Nesta is making a scatterplot of the digit spans (how many numbers you can remember and repeat back) for his psychology class, with the memory for digits the students hear on one axis and the memory for digits the students read on the other. The association is strong, but he notices one student has a visual digit memory that is twice as long as anyone else. Which statistical validity question is he raising?

Could outliers be affecting the relationship?

Mischel (1972) studied delay of gratification in preschoolers: Children were offered a special reward if they could wait or a less attractive treat if they chose not to wait. A follow-up study was done years later, looking at the same children as adolescents. The researchers found an association between the waiting times of the preschoolers and parents' reports of the same children's behaviors as adolescents. Which of the following is a question one could ask to assess the construct validity of this association?

How well was delay of gratification measured?

Dr. Thompson researches gang-related crime in a large city. She notices 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 graffiti and concludes the ice cream trucks are encouraging graffiti. Her colleague, Dr. Richardson, points out that both ice cream sales and graffiti might be influenced by rising temperatures during the summer. Which kind of problem has Dr. Richardson identified?

a third-variable problem

Professor Fofana wonders if there is an association between students' grades and extra credit points earned in his classes. He first made a scatterplot, with the number of extra credit points earned on the x-axis and the numerical grade in his course without extra credit on the y-axis. He then decides the plot would be clearer if he converted the numerical grades into passing or failing the course, so he plots a bar graph with pass/fail on the x-axis and the mean number of extra credit points earned on the y-axis. Which type of statistic would he run to determine if there is a relationship between pass/fail and extra credit points earned?

t test

Vida is studying the connection between school grades and time spent using social media. She finds a strong correlation, showing students with lower grades spend more time using social media. She decides that before she can claim increased use of social media causes grades to drop, she must make sure the social media came before the low grades. Which criterion of causality is she concerned with?

temporal precedence