Chapters 1-14 psych 261

What sample size is often cited as the optimal balance between accuracy and effort?

1,000

Psychological scientists base their conclusions on the evidence. They collect data and use it to develop, support, or challenge a theory. This approach is known as ____________.

empiricism

How many possible orders for full counterbalancing are there in a study with four conditions?

24

________ is when you study every member of a population.

A census

____________ is an extra dependent variable that can be used to help researchers quantify how well an experimental manipulation worked.

A manipulation check

__________ is a simple study that uses a separate group of participants that is generally completed before conducting the study of primary interest in order to confirm the effectiveness of a manipulation.

A pilot study

Which of the following is a common way that journalists misrepresent science when they write about it for a popular audience?

exaggerating the strength of the findings

Participants in a research study are given a list of words to study for 3 minutes and then, following a delay, are asked to recall the list. The length of the delay is manipulated between participants to be either 2 minutes, 5 minutes, or 10 minutes. Which of the following scenarios would present a design confound in this experiment?

All participants in the 2-minute condition are tested at 8:00 a.m.; those in the 5-minute condition are tested at noon; and those in the 10-minute condition are tested at 4:00 p.m.

What is one way to avoid being misled by journalism reports on scientific research?

Consult the source of the article — the original scientific findings.

Daniel's teacher tells him that his theory about dating is not strong because it is not falsifiable. What does she mean?

Daniel's theory cannot be disproven.

Which of these is NOT a potential drawback of a within-groups design?

Extraneous differences are held constant across conditions.

Dr. Rhodes is interested in how differing levels of light affect how people perceive color. He finds participants for this research study by making an announcement in several psychology classes at his university. Should Dr. Rhodes be concerned about using this sampling method?

No, because external validity probably doesn't matter for the type of claim he is making.

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 relation between waiting time as a preschooler and self-control in adolescence emerged. Can a causal relationship be inferred?

No, because internal validity was not established.

Dr. Lawrence is the director of Counseling Services at her university. She is planning to conduct a survey of 100 students at the university to see how aware they are of the counseling services that are offered at the university. She wants the proportion of males and females in her sample to reflect the proportion in the university as a whole (55 percent female and 45 percent male). Dr. Lawrence plans to stand in the Student Union and ask people to participate until she has given the survey to 55 females and 45 males. Is Dr. Lawrence collecting a representative sample?

No, because the participants are selected nonrandomly.

Which of the following is NOT a method for addressing concerns about external validity in a small-N study?

Nothing — it is not possible to achieve external validity in small-N design.

Which of the following is true of publishing in the field of psychology?

Publishing in psychology involves a peer-review process.

Which of the following does NOT characterize a small-N design?

Results are analyzed in terms of statistical significance.

Julie works at a large gym. She wants to do a study of the effect of having a personal trainer on self-esteem and mood. She collects a list of members at her gym who would like to have a personal trainer. She assigns half of them to have a trainer right away and half of them to wait several months before being assigned a trainer. She measures self-esteem and mood in all of the participants over the next several months when only one of the groups would have a trainer. What advantages does Julie's design have over selecting a group of people at the gym who were already using personal trainers and a group who were not using trainers?

She is preventing a selection effect.

Franchesca read about Elliot et al.'s (2007) study in which students scored lower on a cognitive test when the test had a red booklet cover. Franchesca is interested in the idea that the color red influences the perception of caution. Franchesca decides to conduct a similar study in which she has students rate themselves on several achievement-related characteristics, including critical reasoning skills, vocabulary, and math ability. Like the original study, the students write their self-ratings in booklets of either red, green, or white color. Franchesca predicts that, in line with the original study, students with red booklets would rate themselves lower than students with white or green booklets. Franchesca runs the study and finds that the results match her prediction. The data matched Franchesca's prediction. What conclusion can Franchesca make?

The data support the theory.

Some theories are better than others. Which of the following is NOT considered a feature of a good theory?

The theory makes sense intuitively.

When the data from a study do not support the theory behind the study's hypothesis, what does that mean for the theory?

The theory should be revised.

Dr. Stevens wants to examine the relationship between body mass index (BMI) and depression. He selects a sample of American athletes who are currently training for the summer Olympic Games as his research subjects. Dr. Stevens finds no relationship between BMI and depression. What 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 characteristics sets scientific journals apart from magazines?

They are peer-reviewed.

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

They involve two measured variables.

Mr. Stratford is the president of a national organization of lesbian, bisexual, gay, and transgender people in the United States. He wants to survey 1,000 members of his organization about the position they want the organization to take on several political issues. He knows that transgender people make up only 5 percent of his organization, but he wants to make sure that their views are accurately represented. He decides that he will randomly sample 100 transgender members and then adjust the final results so that transgender people are weighted to their actual proportion in the organization. Is Mr. Stratford collecting a representative sample?

Yes, because the transgender people in the final sample were sampled randomly from the population of transgender people in the organization.

Seligman (1975, 1991) proposed that animals who cannot escape an aversive outcome don't even try to avoid the aversive experience later, when they can escape it, because they don't perceive themselves as having control ("learned helplessness"). Latecia thinks this concept may apply to people's working conditions. She conducts a study and has 20 research participants work in an office space with some dilapidated supplies (e.g., pens that barely write, crumpled papers). The participants are split into two rooms. In one work room, Latecia offers to replace any of the run-down supplies with newer items. In another work room, Latecia tells the participants that they have to work with what they have. After a few days of working with this set-up, both groups' work spaces now include both the old supplies as well as new supplies. Latecia predicts that the participants who had to work with the dilapidated supplies for the first few days of the study will continue to use the less functional supplies on the last day, even when there are new supplies available in the room. Latecia's prediction that "the participants who had to work with the dilapidated supplies for the first few days of the study will continue to use the less functional supplies on the last day" would best be described as which of the following?

a hypothesis

Which of the following is NOT a way that a researcher might indicate a statistically significant result in a journal article?

a notation of p = .20

What kind of sample is best for external validity?

a sample where each member of the population has an equal chance of being selected

Which of the following is an example of basic research?

a study investigating whether children of divorced parents are more likely to be divorced themselves

Seligman (1975, 1991) proposed that animals who cannot escape an aversive outcome don't even try to avoid the aversive experience later, when they can escape it, because they don't perceive themselves as having control ("learned helplessness"). Latecia thinks this concept may apply to people's working conditions. She conducts a study and has 20 research participants work in an office space with some dilapidated supplies (e.g., pens that barely write, crumpled papers). The participants are split into two rooms. In one work room, Latecia offers to replace any of the run-down supplies with newer items. In another work room, Latecia tells the participants that they have to work with what they have. After a few days of working with this set-up, both groups' work spaces now include both the old supplies as well as new supplies. Latecia predicts that the participants who had to work with the dilapidated supplies for the first few days of the study will continue to use the less functional supplies on the last day, even when there are new supplies available in the room.

a theory

Which of the following could be considered a source of empirical evidence?

a thermometer

Research done specifically to add to our general understanding of psychology is known as ______________.

basic research

Which of these is NOT an advantage of within-groups designs?

elimination of practice effects

A political research center obtains a list of phone numbers for all registered voters in Texas and uses a random number generator to select 1,000 of the phone numbers to call. They ask each voter which gubernatorial candidate they plan to vote for in the upcoming election. What is the population of interest that the research center wants to generalize to?

all registered voters in Texas

What type of research is done with a practical problem in mind?

applied research

A school district is comparing two reading programs for high school students reading below grade level. Two very similar schools are used to test the programs, a different one at each school. Students participating in the programs are pretested for their reading abilities and the mean scores are similar at both schools. The reading program implemented at High School A is known to be much more rigorous than the program implemented at High School B. The posttest shows more improvement at High School A, but more of the students dropped out of the program. What threat to internal validity does this pose?

attrition

In a quasi-experiment by Minke (2011), the effectiveness of Skejby, a Danish half-way house which mixes offenders with non-offenders, was compared to that of the control condition of half-way houses housing only offenders. Measurement of effectiveness was based on rate of recidivism of former inmates. If those inmates who were sent to prison from their half-way houses for violations were not included in the recidivism measurement, which threat to internal validity would this potentially pose?

attrition

In a business class experiment on the endowment effect, Theo is comparing the value of a coffee mug to someone who owns it and is selling it to someone who is buying it. The endowment effect describes the tendency of sellers to value something they own more than buyers do. Participants are randomly assigned to be buyers or sellers of a mug with their first name on it. Buyers select the maximum price they would pay for the mug. Sellers select the minimum price they would accept for the mug. How does Theo control for selection effects?

by using random assignment of participants

The superintendent of schools in a small town in Ohio made a lot of policy changes to the way school administration worked in his district. A researcher at a nearby university wanted to look at what teachers in his district thought about the changes. The researcher made a list of all of the schools in the district and used a random number generator to select a sample of five schools from the district. Then the researcher interviewed every teacher at each of those five schools. What sampling method did the researcher use?

cluster sampling

What is the name for the level of the independent variable that is intended to represent a neutral condition?

control group

What is the name for a variable that the experimenter holds constant on purpose?

control variable

Dr. Rhodes is interested in how differing levels of light affect how people perceive color. He finds participants for this research study by making an announcement in several psychology classes at his university. What kind of sampling method is Dr. Rhodes using?

convenience sampling

Which of the following is considered a biased sampling method?

convenience sampling

Eric designs a study to examine drink preferences of university freshmen. He is planning to have all of the freshmen who participate in his study drink a cup of coffee then rate their enjoyment of the coffee, then drink a cup of tea and rate their enjoyment of the tea, and finally drink a cup of milk and rate their enjoyment of the milk. Eric tells Theresa about the plans for his study and she says she is concerned that he could have a problem with order effect in his study. How can Eric fix this problem?

counterbalancing

Dimitri is interested in understanding the effects of sleep deprivation on short-term memory. Which of the following is an empirical approach Dimitri could take to answer this question?

design and execute a study which measures short-term memory function following different amounts of sleep

In psychology lab, Tetiana is conducting an experiment on depth perception using the Howard-Dolman box. Inside the box are two vertical rods and a horizontal ruler. The participant manipulates the rods until they appear to be aligned at the same distance away, then the experimenter measures how far out of alignment they are. There are three conditions: left eye only, right eye only, and both eyes. Tetiana is using a repeated-measures design. What is the dependent variable in this experiment?

distance out of alignment of the rods

A drought in California created the opportunity for a quasi-experiment on the effectiveness of fines on water conservation (Agras et al., 1980). Three comparable cities were considered: two that instituted fines at different times and a third that did not. Water consumption data for the three years before the onset of the fines was used as baseline and subsequent consumption data was gathered through the end of the drought. Effectiveness of fines was assessed by examining consumption the following month. In this study, researchers capitalized on real-life opportunities to study phenomena. Therefore, they maximized which type of validity?

external

In psychology lab, Tetiana is conducting an experiment on depth perception using the Howard-Dolman box. Inside the box are two vertical rods and a horizontal ruler. The participant manipulates the rods until they appear to be aligned at the same distance away, then the experimenter measures how far out of alignment they are. There are three conditions: left eye only, right eye only, and both eyes. Tetiana is using a repeated-measures design. What is the independent variable in this experiment?

eye/eyes used

Which of these is NOT a reason for a researcher to select a quasi-experimental design?

improved internal validity

In quasi-experiments, researchers lack full experimental control. Therefore, which type of validity must they assess to make sure they can draw firm conclusions from their results?

internal

Which type of validity is typically not relevant to association claims?

internal

Following implementation of a new city law, a restaurant chain began displaying the nutrition labels for their menu items. The restaurant owner recorded sales of the 15 highest-calorie menu items on three occasions—once the month before the change in menu display, once the week of the change in menu display, and once the month after the change in menu display. The owner observed that the sale of the high-calorie menu items dropped, while overall sales remained steady. What type of design is this?

interrupted time-series design

de Abreu, Gathercole, and Martin (2011) found that the correlation of non-word repetition and digit recall in a memory was r = .59. Based on Cohen's (1992) guidelines, how would you describe this effect size?

large

In an experiment, researchers:

manipulate one variable and measure another.

Which of the following is primarily a consumer of research information?

marriage and family counselor

Kathryn wants to control for intelligence in her study. She has a list of all of the participants for her study and their IQ scores. She sorts the list of participants according to their IQ scores and then forms groups making sure that the groups are balanced in terms of IQ scores. Finally, she randomly assigns each group to one of the conditions of her study. What kind of design is Kathryn using?

matched-groups

Gathercole and Baddeley (1990) examined phonological memory skills in children with disordered language development using two control groups, one made up of much younger children who were matched on verbal abilities. If they had done a follow-up study a year later, which type of threat to internal validity would this age difference most likely have caused?

maturation

Following implementation of a new city law, a restaurant chain began displaying the nutrition labels for their menu items. The restaurant owner recorded sales of the 15 highest-calorie menu items on three occasions—once the month before the change in menu display, once the week of the change in menu display, and once the month after the change in menu display. The owner observed that the sale of the high-calorie menu items dropped, while overall sales remained steady. What is the independent variable in this study?

menu labeling

According to Cohen's conventions for effect size, how do you describe an effect size when d = 0.50?

moderate

A drought in California created the opportunity for a quasi-experiment on the effectiveness of fines on water conservation (Agras et al., 1980). Three comparable California cities were considered: two that instituted fines at different times and a third that did not institute fines. Water consumption data for the three years before the onset of the fines was used as baseline and subsequent consumption data was gathered through the end of the drought. Effectiveness of fines was assessed by examining consumption the following month. With regard to the monitoring of water consumption, what type of design was this?

multiple baseline

A psychologist is working with the parents of four children who exhibit violent behaviors toward each other. The parents have been instructed to record the number of these behaviors each child exhibits in the pre-dinner hour for one week. The parents then begin using a positive reinforcement technique to shape the behavior of the youngest child, while continuing to record. The recording continues and the technique is used on one additional child each week. By the end of six weeks, there is a significant decrease in violent behaviors for each of the children. What type of design is this?

multiple-baseline

The campus safety committee has asked Professor Ibrahim to study bicycling on his campus. He trains two observers and has them observe the number of cyclists and their safety at various points around campus. He selects ten observation locations at random from the places bicycles can be ridden on campus and five one-hour spans of time at random from the daylight hours for each place. He has his observers make observations at each of the ten places for each of the five time spans. What type of sampling is he using?

multistage sampling

What is the term for a quasi-experimental design with at least one treatment group and one comparison group, but in which the participants have not been randomly assigned to the groups?

nonequivalent control group design

A company that owned several hospitals in rural areas of the south went bankrupt and closed the hospitals it operated over a period of a couple of months. Researchers became aware of this situation and used public health records to document average age at death of residents in those communities where the hospitals closed and in communities that were matched on several variables but did not lose their hospitals. The researchers collected death records for several years before and after the closure of these hospitals to look at the effect the closure had on life expectancy. What kind of research design are the researchers using?

nonequivalent control group interrupted time-series design

"All other things being equal, the simplest solution is the best." Which principle does this describe?

parsimony

Dr. Keller wants to test the effect of a new anti-anxiety medication. He recruits a group of anxious patients and randomly assigns them to two groups. One group will receive his new medication and the other will receive a sugar pill. What is the second group called?

placebo group

A ________ is the entire set of people in which the researchers are interested.

population

What design is an experiment in which each participant is randomly assigned to one level of the independent variable and then tested on the dependent variable once?

post-test only

Cara is running a study to examine the effect of music on mood. She randomly assigns participants to three conditions — rock, jazz, and country. She has the participants rate their mood with a short questionnaire, then listen to their assigned music for 20 minutes, and then fill out the mood questionnaire again. What kind of design is she using?

pretest/posttest

Dr. Jennings is doing a study on the experience of being a racial minority on a college campus. He goes to the Asian Student Association, Black Student Union, and Hispanic Student Group on his campus to recruit participants for his study. Dr. Jennings only includes Asians, African-Americans, and Hispanic participants in his study. What type of sampling is Dr. Jennings using?

purposive sampling

Dr. Lawrence is the director of Counseling Services at her university. She is planning to conduct a survey of 100 students at the university to see how aware they are of the counseling services that are offered at the university. She wants the proportion of males and females in her sample to reflect the proportion in the university as a whole (55 percent female and 45 percent male). Dr. Lawrence plans to stand in the Student Union and ask people to participate until she has given the survey to 55 females and 45 males. What type of sampling method is Dr. Lawrence going to use?

quota sampling

Which of the following is most important for enhancing external validity?

random sampling

Which of the following is NOT a way that researchers in a quasi-experimental study attempt to achieve internal validity?

randomly assigning participants to conditions

In a quasi-experiment by Minke (2011), the effectiveness of Skejby, a Danish half-way house which mixes offenders with non-offenders, was compared to that of the control condition of half-way houses housing only offenders. Measurement of effectiveness was based on rate of recidivism of former inmates. What was the dependent variable in this study?

rate of recidivism

Eric designs a study to examine drink preferences of university freshmen. He is planning to have all of the freshmen who participate in his study drink a cup of coffee then rate their enjoyment of the coffee, then drink a cup of tea and rate their enjoyment of the tea, and finally drink a cup of milk and rate their enjoyment of the milk. What kind of design is this?

repeated measures

Ellen is an elementary school teacher who has a very disruptive child in her classroom. She wants to see whether using a good behavior point system will be effective for managing this child's behavior. She begins by noting the child's behavioral outbursts for a week before she begins the point system, then she tries using the point system for two weeks and notices a drop in the child's outbursts. For the next two weeks she discontinues using the point system and she notes an increase in the child's outburst. What kind of design is Ellen using to test this intervention?

reversal

In a business class experiment on the endowment effect, Theo is comparing the value of a coffee mug to someone who owns it and is selling it to someone who is buying it. The endowment effect describes the tendency of sellers to value something they own more than buyers do. Participants are randomly assigned to be buyers or sellers of a mug with their first name on it. Buyers select the maximum price they would pay for the mug. Sellers select the minimum price they would accept for the mug. What is the independent variable in this experiment?

role of the participant

Following implementation of a new city law, a restaurant chain began displaying the nutrition labels for their menu items. The restaurant owner recorded sales of the 15 highest-calorie menu items on three occasions—once the month before the change in menu display, once the week of the change in menu display, and once the month after the change in menu display. The owner observed that the sale of the high-calorie menu items dropped, while overall sales remained steady. What is the dependent variable in this study?

sales for high-calorie menu items

In a nonequivalent control group design, participants in the control group may match the treatment group on an important factor. Which internal validity threat is this?

selection

In a quasi-experiment by Minke (2011), the effectiveness of Skejby, a Danish half-way house which mixes offenders with non-offenders, was compared to that of the control condition of half-way houses housing only offenders. Measurement of effectiveness was based on rate of recidivism of former inmates. If inmates are allowed to choose their own half-way house, which threat to internal validity would this potentially pose?

selection

Participants in a research study are given a list of words to study for 3 minutes and then, following a delay, are asked to recall the list. The length of the delay is manipulated between participants to be either 2 minutes, 5 minutes, or 10 minutes. Since different groups need different amounts of time, the first 25 participants who arrive are assigned to the 10-minute group, the next 25 are assigned to the 5-minute group, and the final 25 are assigned to the 2-minute group. What confound does this create?

selection effect

Which of the following does NOT need to be considered as an alternative explanation of the results in a within-groups design experiment?

selection effects

Two universities are involved in a study of the effects on student retention and attitude toward campus life based on a pre-freshman year summer visit program that one of the schools had implemented. The schools, both state universities in the same state, were closely matched in student body characteristics. In the fall of the first year of the program, the school that was serving as the control was struck by a rare fall tornado, which did damage to several campus buildings. What type of threat to internal validity would this cause?

selection-history

A political research center obtains a list of phone numbers for all registered voters in Texas and uses a random number generator to select 1,000 of the phone numbers to call. They ask each voter which gubernatorial candidate they plan to vote for in the upcoming election. What sampling method is being used?

simple random sampling

A sample is always __________ a population.

smaller than

Beth is working on a research study focused on attention span in children. Among the participants, the group of 11-year-old boys is underrepresented. Beth asks her 11-year-old brother to distribute flyers about participation in the study to his male classmates and soccer team. What type of sampling is this?

snowball

A study by Grimstvedt et al. (2010) of the effects of signage on stair use in university buildings examined the effect of placing signs encouraging stair use near elevators. Based on their design, Blake is designing a study for her campus. The initial part of the study will be a month-long measuring of elevator and stair use in four different buildings on the campus. This will be followed by the treatment: the simultaneous posting of signs at each of the four locations. Elevator and stair use will then be measured for another month. What type of design is this?

stable-baseline

A college administrator knows that 70 percent of the students at his college are from out of state, so he decides to make sure that he includes 70 out-of-state students and 30 in-state students in his survey about admission practices at the college. He has a list of all of the out-of-state and all of the in-state students currently enrolled at the college. He randomly selects 70 students from the out-of-state list and 30 students from the in-state list. What sampling method is he using?

stratified random sampling

In psychology lab, Tetiana is conducting an experiment on depth perception using the Howard-Dolman box. Inside the box are two vertical rods and a horizontal ruler. The participant manipulates the rods until they appear to be aligned at the same distance away, then the experimenter measures how far out of alignment they are. There are three conditions: left eye only, right eye only, and both eyes. Tetiana is using a repeated-measures design. She finds that d = 1.53. What effect size is this?

strong

Which of the following is considered a representative sampling method?

systematic sampling

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 decides the plot will be clearer if he converts the numerical grades into letter grades and plots a bar graph with letter grades on the x-axis and the mean number extra credit points earned on the y-axis. What type of statistic would he run to determine if there is a relationship between letter grades and extra credit points earned?

t test

To look at the relationship between reaction time and level of expertise in tennis, experts and non-experts are 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

Researchers are conducting a repeated-measures quasi-experiment. What type of threat to internal validity should concern the researchers if they notice the participants are taking less and less time to complete the assessment questionnaires that are administered weekly?

testing

Franchesca read about Elliot et al.'s (2007) study in which students scored lower on a cognitive test when the test had a red booklet cover. Franchesca is interested in the idea that the color red influences the perception of caution. Franchesca decides to conduct a similar study in which she has students rate themselves on several achievement-related characteristics, including critical reasoning skills, vocabulary, and math ability. Like the original study, the students write their self-ratings in booklets of either red, green, or white color. Franchesca predicts that, in line with the original study, students with red booklets would rate themselves lower than students with white or green booklets. Franchesca runs the study and finds that the results match her prediction.

the peer-review process

Franchesca read about Elliot et al.'s (2007) study in which students scored lower on a cognitive test when the test had a red booklet cover. Franchesca is interested in the idea that the color red influences the perception of caution. Franchesca decides to conduct a similar study in which she has students rate themselves on several achievement-related characteristics, including critical reasoning skills, vocabulary, and math ability. Like the original study, the students write their self-ratings in booklets of either red, green, or white color. Franchesca predicts that, in line with the original study, students with red booklets would rate themselves lower than students with white or green booklets. Franchesca runs the study and finds that the results match her prediction. Which of the following is the data in this study?

the self-ratings of the students

Franchesca read about Elliot et al.'s (2007) study in which students scored lower on a cognitive test when the test had a red booklet cover. Franchesca is interested in the idea that the color red influences the perception of caution. Franchesca decides to conduct a similar study in which she has students rate themselves on several achievement-related characteristics, including critical reasoning skills, vocabulary, and math ability. Like the original study, the students write their self-ratings in booklets of either red, green, or white color. Franchesca predicts that, in line with the original study, students with red booklets would rate themselves lower than students with white or green booklets. Franchesca runs the study and finds that the results match her prediction. Franchesca's process of conducting a study to evaluate whether the influence of the color red extends to self-ratings can best be described as which of the following?

the theory-data cycle

A statement, or set of statements, that describes general principles about how variables relate to one another is a ________________.

theory

Which of the following outlines the correct order of steps in the theory-data cycle?

theory, research design, hypothesis, data

After reading about Harlow's contact comfort theory, Dr. Borden wonders if these findings would apply to touch and cuddling speeding up weight gain in premature babies in the neonatal intensive care unit. He designs a study to test this idea. What type of research is Dr. Borden's study?

translational research

In psychology lab, Tetiana is conducting an experiment on depth perception using the Howard-Dolman box. Inside the box are two vertical rods and a horizontal ruler. The participant manipulates the rods until they appear to be aligned at the same distance away, then the experimenter measures how far out of alignment they are. There are three conditions: left eye only, right eye only, and both eyes. Tetiana is using a repeated-measures design. How is the independent variable being manipulated in Tetiana's design?

within-groups