BESC 3020 CH. 10

Two-independent-sample t test or independent-sample t test

a statistical procedure used to test hypotheses concerning the difference in interval or ratio scale data between two group means, in which the variance in the population is unknown.

Control

(a) the manipulation of a variable and (b) holding all other variables constant. When control is low, neither criterion is met; when control is high, both criteria are met.

Which of the following is an example of an experimental manipulation for the level of phone use among participants?

*NOT* A researcher asks participants to report how often they use a phone and then uses that data to group participants in to those who are low or high phone users.

A researcher measures locomotor activity among rats placed in a cage with high or low lighting. What type of manipulation was used in this study?

*NOT* A staged manipulation

A researcher conducts two experiments. In Experiment 1, he manipulates whether participants receive a small, medium, or large reward for each item recalled in an assessment. In Experiment 2, he manipulates whether participants receive a small, medium, or large punishment for each item not recalled in an assessment. The mean difference between groups is the same in each experiment, but Experiment 2 is associated with greater error variance. In which experiment is the researcher more likely to conclude that the mean difference is caused by individual differences?

*NOT* Neither experiment

When most scores in each group of an experiment do overlap, then all of the following are true except:

*NOT* the power to detect mean differences between groups will be low.

Error variance or error

A numeric measure of the variability in scores that can be attributed to or is caused by the individual differences of participants in each group

Between-subjects design

A research design in which different participants are observed one time in each group or at each level of a factor.

Pairwise comparison

A statistical comparison for the difference between two group means. A post hoc test evaluates all possible pairwise comparisons for an ANOVA with any number of groups.

Post hoc test

A statistical procedure computed following a significant ANOVA to determine which pair or pairs of group means significantly differ. These tests are needed with more than two groups because multiple comparisons must be made.

One-way between-subjects ANOVA

A statistical procedure used to test hypotheses for one factor with two or more levels concerning the variance among group means. This test is used when different participants are observed at each level of a factor and the variance in a given population is unknown.

Between-subjects factor

A type of factor in which different participants are observed in each group, or at each level of the factor,

Self-report measure

A type of measurement in which participants respond to one or more questions or statements to indicate their actual or perceived experiences, attitudes, or opinions.

Behavioral measure

A type of measurement in which researchers directly observe and record the behavior of subjects or participants.

Physiological measure

A type of measurement in which researchers record physical responses of the brain and body in a human or an animal.

Control by matching

A type of restricted random assignment in which we assess or measure the characteristic we want to control, group or categorize participants based on scores on that measure, and then use a random procedure to assign participants from each category to a group in the study.

Control by holding constant

A type of restricted random assignment in which we limit which participants are included in a sample based on characteristics they exhibit that may otherwise differ between groups in a study.

A researcher conducts a clinical trial to determine the effectiveness of a behavioral strategy used to reduce overall caloric intake. Because men consume many more calories than women and because women are more likely to diet than men, the researcher decides to only include women in the clinical trial. What type of restricted random assignment was used in this example?

Control by holding constant

A researcher conducts a between-subjects experimental research design and measures a mean difference in the dependent measure between two groups. How can the researcher test if the mean difference observed in his sample is due to individual differences or due to the manipulation made by the researcher?

Compute a two-independent sample t-test

Random assignment is a procedure used to ensure that each participant, and therefore the _____________, are assigned to groups by chance.

individual differences of participants

A researcher creates two groups. In one group, children played with a toy that made noise. In a second group the children played with the same toy but it did not make noise. The time spent playing with each toy was recorded. The control group in this example is:

the group in which the toy did not make noise.

Experimental group or treatment group

A condition in an experiment in which participants are treated or exposed to a manipulation, or level of the independent variable, that is believed to cause a change in the dependent variable.

Test Statistic

A mathematical formula that allows researchers to determine the extent to which differences observed between groups can be attributed to the manipulation used to create the different groups.

Restricted random assignment

A method of controlling differences in participant characteristics between groups in a study by first restricting a sample based on known participant characteristics, then using a random procedure to assign participants to each group. Two strategies of restricted random assignment are control by matching and control by holding constant.

Between-subjects experimental design

An experimental research design in which the levels of a between-subjects factor are manipulated, then different participants are randomly assigned to each group or to each level of that factor, and observed one time

Placebo

An inert substance, surgery, or therapy that resembles a real treatment but has no real effect.

How do researchers account for individual differences in an experiment, methodologically?

By using random assignment to make individual differences about the same in each group.

What are the three requirements for a between-subjects design to be an experimental research design?

Randomization, manipulation, and comparison

Which of the following is NOT a step for conducting a between-subjects experimental design?

Randomly assign participants to different levels of the dependent variable.

Two researchers studied the effects of cell phone use on attention. Researcher 1 randomly assigned participants to watch a short video clip while holding a cell phone that was turned off or while talking on a cell phone with a confederate. Researcher 2 grouped participants based on whether they reported high or low cell phone use, then had participants complete an attention-demanding task. Which researcher used a type of sampling that is commonly used in experiments?

Researcher 1

Two researchers investigated studying behavior among college students. Researcher 1 had the same participants study with a partner and then without a partner. Researcher 2 had participants study with a partner and a different group of participants study without a partner. Which researcher selected an independent sample?

Researcher 2

Experimental manipulation

The identification of an independent variable and the creation of two or more groups that constitute the levels of that variable.

Natural manipulation

The manipulation of a stimulus that can be naturally changed with little effort.

Stages manipulation

The manipulation of an independent variable that requires the participant to be "set up" to experience some stimulus or event.

Independent sample

Where different participants are independently observed one time in each group.

A condition in an experiment in which participants are treated or exposed to a manipulation, or level of the independent variable, that is believed to cause a change in the dependent variable is called:

an experimental group.

A type of factor in which different participants are observed in each group, or at each level of the factor, is called:

between-subjects factor.

A type of restricted random assignment in which we limit which participants are included in a sample based on characteristics they exhibit that may otherwise differ between groups in a study is called:

control by holding constant.

A type of restricted random assignment in which we assess or measure the characteristic we want to control, group or categorize participants based on scores on that measure, and then use a random procedure to assign participants from each category to a group in the study is called:

control by matching.

The more that scores in each group ________, the larger the error variance.

overlap

A statistical comparison for the difference between two group means is called:

pairwise comparison.

The less that scores overlap between groups, the ________ the error variance.

smaller