PSY 3213 Ch. 10: Intro to Simple Experiments Inquizitive

comparison group

A group in an experiment whose levels on the independent variable differ from those of the treatment group in some intended and meaningful way. Also called comparison condition. (page 279)

control group

A level of an independent variable that is intended to represent "no treatment" or a neutral condition. Also called control condition. (page 280)

full counterbalancing

A method of counterbalancing in which all possible condition orders are represented. See also counterbalancing, partial counterbalancing. (page 295)

partial counterbalancing

A method of counterbalancing in which some, but not all, of the possible condition orders are represented. See also counterbalancing, full counterbalancing. (page 296)

pilot study

A study completed before (or sometimes after) the study of primary interest, usually to test the effectiveness or characteristics of the manipulations. (page 300)

experiment

A study in which one variable is manipulated and the other is measured. (page 276)

Match each term to the correct description. replication pilot study counterbalancing manipulation check a. an extra dependent variable that can be used to help researchers evaluate how well an experimental manipulation worked b. conducting multiple studies on the same question to get more precise estimates c. presenting the levels of the independent variable to participants in different sequences d. study completed separately from the main study to confirm the effectiveness of a manipulation

a. manipulation check b. replication c. counterbalancing d. pilot study

To establish a causal claim, researchers often prioritize ___ validity over ___ validity. While researchers hope to ___ their findings to other people and settings, in experiments, they focus more on ensuring the independent variable does not accidentally ___ with another variable. statistical unsystematically vary systematically vary external generalize construct internal replicate

internal, external, generalize, systematically vary

placebo group

A control group in an experiment that is exposed to an inert treatment, such as a sugar pill. Also called placebo control group. (page 280)

demand characteristic

A cue that leads participants to guess a study's hypotheses or goals; a threat to internal validity. Also called experimental demand. (page 297)

Latin square

A formal system of partial counterbalancing to ensure that every condition in a within-groups design appears in each position at least once. (page 296)

confound

A general term for a potential alternative explanation for a research finding; a threat to internal validity. (page 281)

design confound

A threat to internal validity in an experiment in which a second variable happens to vary systematically along with the independent variable and therefore is an alternative explanation for the results. (page 282)

selection effect

A threat to internal validity that occurs in an independent-groups design when the kinds of participants at one level of the independent variable are systematically different from those at the other level. (page 284)

practice effect

A type of order effect in which participants' performance improves over time because they become practiced at the dependent measure (not because of the manipulation or treatment). Also called fatigue effect. See also order effect, testing threat. (page 294)

carryover effect

A type of order effect, in which some form of contamination carries over from one condition to the next. (page 294)

measured variable

A variable in a study whose levels (values) are observed and recorded. (page 277)

manipulated variable

A variable in an experiment that a researcher controls, such as by assigning participants to its different levels (values). (page 276)

concurrent-measures design

An experiment using a within-groups design in which participants are exposed to all the levels of an independent variable at roughly the same time, and a single attitudinal or behavioral preference is the dependent variable. (page 291)

repeated-measures design

An experiment using a within-groups design in which participants respond to a dependent variable more than once, after exposure to each level of the independent variable. (page 290)

posttest-only design

An experiment using an independent groups design in which participants are tested on the dependent variable only once. Also called equivalent groups, posttest-only design. (page 287)

pretest/posttest design

An experiment using an independent-groups design in which participants are tested on the key dependent variable twice: once before and once after exposure to the independent variable. (page 288)

independent-groups design

An experimental design in which different groups of participants are exposed to different levels of the independent variable, such that each participant experiences only one level of the independent variable. Also called between-subjects design or between-groups design. (page 287)

within-groups design

An experimental design in which each participant is presented with all levels of the independent variable. Also called within-subjects design. (page 287)

matched groups

An experimental design technique in which participants who are similar on some measured variable are grouped into sets; the members of each matched set are then randomly assigned to different experimental conditions. Also called matching. (page 286)

Gokhan wants to examine whether coffee increases productivity. He creates two conditions in his study—2 cups of coffee per day and 2 cups of water per day—and asks his participants to sign up for the condition they prefer. In the morning, participants drink either 2 cups of coffee or 2 cups of water. At the end of the day, participants rate their level of productivity on a scale of 1 ("not productive at all") to 10 ("extremely productive"). Which of the following descriptions are applicable to Gokhan's experiment? selection effect posttest-only design independent-groups design pretest/posttest design random assignment within-groups design

Applicable: posttest-only design independent-groups design selection effect Not Applicable: random assignment pretest/posttest design within-groups design

counterbalancing

In a repeated-measures experiment, presenting the levels of the independent variable to participants in different sequences to control for order effects. See also full counterbalancing, partial counterbalancing. (page 295)

order effect

In a within-groups design, a threat to internal validity in which exposure to one condition changes participant responses to a later condition. See also carryover effect, practice effect, testing threat. (page 294)

systematic variability

In an experiment, a description of when the levels of a variable coincide in some predictable way with experimental group membership, creating a potential confound. (page 282)

unsystematic variability

In an experiment, a description of when the levels of a variable fluctuate independently of experimental group membership, contributing to variability within groups. (page 282)

control variable

In an experiment, a variable that a researcher holds constant on purpose. (page 278)

independent variable

In an experiment, a variable that is manipulated. (page 277)

manipulation check

In an experiment, an extra dependent variable researchers can include to determine how well a manipulation worked. (page 299)

dependent variable

In an experiment, the variable that is measured. Also called outcome variable. (page 277)

condition

One of the levels of the independent variable in an experiment. Also called the predictor variable. (page 277)

power

The likelihood that a study will show a statistically significant result when an independent variable truly has an effect in the population; the probability of not making a Type II error. (page 293)

treatment group

The participants in an experiment who are exposed to the level of the independent variable that involves a medication, therapy, or intervention. (page 280)

random assignment

The use of a random method (e.g., flipping a coin) to assign participants into different experimental groups. (page 284)

Identify the true and false statements about within-groups designs. a. Within-groups designs make it easier to be certain of differences between conditions than independent-groups designs. b. Within-groups designs are always superior to independent-groups designs. c. A within-groups design usually requires fewer participants than an independent-groups design. d. Participants in a within-groups design serve as their own control.

True: a. c. d. False: b.

Identify the true and false statements about experiments. a. If the manipulation of the independent variable causes a change in the dependent variable, covariance is established. b. Every experiment requires a control group. c. Measuring the dependent variable establishes temporal precedence. d. Every experiment requires a comparison group.

True: a. d. False: b. c.

Label each example with the type of variability it best represents: unsystematic variability or systematic variability. Labels can be used more than once. a. Shilpa wants to examine whether time of day affects grocery shoppers' moods. She finds that people who shop for groceries earlier in the day are happier than people who shop later in the evening. After Shilpa collects her data, the manager tells her that the store usually has more items in stock in the morning. b. Travis is comparing the effects of music type on productivity. His research assistants tell him they really enjoy the upbeat music condition. c. Imani and her three research assistants are doing a study on sociability in college students, with participants either in one-on-one or in small groups. She later finds out that one of her research assistants is much chattier than the others in both the one-on-one and small group conditions. d. Marcos is testing how video game performance affects aggression. He randomly assigns participants to play either an easy video game or a difficult video game. Some of his participants have never played video games before.

Unsystematic: c. d. Systematic: a. b.

Label each study with the correct study design. matched-groups design repeated-measures design concurrent-measures design pretest/posttest design a. Rukmini is running a study to examine the effect of music genre on mood. She randomly assigns participants to three conditions: rock, jazz, and country. She has the participants rate their mood, then listen to their assigned music for 20 minutes, and then fill out the mood questionnaire again. b. Jafari wants to control for intelligence in his study. He sorts the list of participants according to their IQ scores and then forms groups, making sure the groups are balanced in terms of IQ scores. Finally, he randomly assigns each group to one of the conditions of his study. c. Terrance wants to find out whether sweet or salty snacks make people more satisfied. He first gives everyone a salty snack and has them rate their level of satisfaction. Then, he gives everyone a sweet snack and has them rate their level of satisfaction again. d. Kiana designs a study to examine the juice preferences of preschool children. She has the children drink a small cup of apple juice and then a small cup of orange juice. She then asks the children which of the two was their favorite.

a. pretest/posttest design b. matched-groups design c. repeated-measures design d. concurrent-measures design

When researchers manipulate a variable in a study, they are carrying out a(n) ___. The manipulated variable is often called the ___ variable. A manipulated variable always has more than one level, or ___. Researchers measure the ___ variable to determine the effect of the manipulated variable on it. Researchers often keep certain other factors constant on purpose. This kind of variable is called a(n) ___. experiment independent treatment dependent placebo condition correlation control

experiment, independent, condition, control

In a within-groups design, each participant experiences all levels of the ___. There are two types of this design. The first is the ___ design, in which researchers expose participants to various levels of the independent variable and measure the dependent variable after each exposure. The second is the ___ design, in which participants interact with the various levels of the independent variable simultaneously. dependent variable concurrent-measures independent variable pretest/posttest posttest-only independent-groups repeated-measures

independent variable, repeated-measures, concurrent measures

Experiments that compare different participants who are placed in different conditions are known as ___ designs. There are two basic forms of this design. The first is the ___ design, in which participants are tested on the dependent variable only once after the manipulation. The second is the ___ design, in which participants are tested on the dependent variable before and after the manipulation. within-groups independent-groups pretest/posttest posttest-only repeated-measures

independent-groups, posttest-only, pretest/posttest

In a within-groups design, exposing participants to one level of the independent variable can change how they respond to the other levels of the independent variable. This problem is generally referred to as a(n) ___, of which there are various types. One specific type is known as a(n) ___. This occurs when exposure to one level of the independent variable contaminates how other levels of the independent variable are perceived. Another type is a(n) ___, which occurs when participants change their responses because of repetition of the dependent variable rather than because of the independent variable itself. It is also possible that repeated exposure to the independent variable may cause participants to guess the hypothesis of the experiment, also known as a(n) ___. design confound counterbalancing demand characteristic selection effect practice effect order effect carryover effect

order effect, carryover effect, practive effect, demand characteristic

When a researcher inadvertently creates a condition with a fundamentally different type of participant than another condition, this can create a ___. Researchers can combat this issue by using ___ to arbitrarily assign participants to each level. In some cases, especially with smaller sample sizes, researchers will deliberately assign participants to groups so that each group has a similar makeup for a particular attribute they are concerned about. This is known as creating ___. random sampling selection effect systematic variability design confound matched groups random assignment

selection effects, random assignment, matched groups

What criterion for causation is clearly established by manipulating the independent variable? temporal precedence covariance internal validity

temporal precedence