Quiz 4 Psych

What needs to happen in order to do a correlation.

1. relationship: no independent and dependent variables —> association between variable X and variable Y 2. Two variables 3. Continuous Variables So far —> categorical variables: z-test, t-test, ANOVAs two continuous variables: correlation

Effects of stress, caffeine, difficulty on test performance. Is what kind of Factorial ANOVA

2 x 2 x 2

In a 2 x 2 x 2 factorial ANOVA, how many factors does a researcher study?

3

In a 3 x 3 factorial ANOVA, how many levels do the factors have?

3

Effects of stress, caffeine, difficulty on test performance. What are the Factors and Levels?

3 Factors, A) Stress B) Caffeine C) Difficulty Stress: Low vs High, 2 levels Caffeine: 1 cup vs. none, 2 levels Difficulty: Easy vs. hard, 2 levels. 3 factors, each with 2 levels. 2 x 2 x 2

Factorial ANOVA example. Classroom environment and learning. Factor 1: Task modality level 1: reading level 2: listening. Factor 2: Environment (lighting, sound, temp). level 1: normal. Level 2: outside comfort zone. Dependent Variable: passage comprehension. What is the null hypotheses?

3 questions = 3 null hypothesis 1. Main effect of Factor 1 Does task modality affect passage? H0: µA1 = µA2 -> H1: µA1 ≠ µA2 2. Main effect of Factor 2: Does the environment affect passage comprehension? H0: µB1 = µB2 —> There is no main effect of factor B H1: µB1 ≠ µB2—> There is a main effect of factor B 3. Interaction between factor A and B Does the effect of task modality on passage comprehension depend on the environment? H0: There is no interaction between factors A and B H1: There is an interaction between factors A and B

How many groups of participants would you have in a 2 x 2 factorial ANOVA with independent-samples design?

4

Dr Rivera is conducting a 2 x 4 independent-groups factorial design. How many independent variables are his study? A) 2 B) 4 C)8

A) 2

Dr. Cheng is conducting a 2 x 2 x 2 independent groups factorial design. How many levels each of her independent variables has? A) 2 B) 3 C) 4

A) 2

Dr. Heineken is conducting a 2 x 4 independent groups factorial design. How many main effects will he need to examine? A) 2 B) 4 C) 8

A) 2

Dr. Longoria is conducting a 2 x 2 x 2 independent groups factorial design. How many independent variables does she have? A) 2 B) 3 C) 4

C) 3

Dr. Javier is conducting a 2 x 2 x 3 independent-groups factorial design. How many interactions will he need to examine? A) 2 B) 3 C) 4

C) 4

Dr. Welsh is conducting a 2 x 4 independent groups factorial design. How many groups of participants does she need? A) 2 B) 4 C) 8

C) 8

Dr. Heinz would like to examine the effects of different types of instruction on piano playing skills of young children. One group gets sheet reading instructions, one group gets Suzuki training, and the third gets online instructions. At the end of the training, a piano teacher assesses the students piano performance. To analyze the data, he can use. a) both an independent samples t-test and a one way ANOVA b) both a repeated samples t-test and a repeated measures ANOVA. c) a one way ANOVA d) a repeated measures ANOVA e) a factorial ANOVA

C) a one way ANOVA

A human-factors psychologist is comparing two computer keyboard designs. Half of the participants are assigned to the Keyboard 1 condition, and the other half are assigned to the Keyboard 2 condition. Both groups are given material to type on a particular keyboard, and the number of errors committed by each participant is recorded. Which statistical test would be the best to analyze the data? A) independent-samples t-test B) one-way ANOVA C) both A and B

C) both A and B

3 x 2 Factorial ANOVA example.

Effects of color and label on children's toy preferences. Factor 1: Color, Levels: Pink, Blue, Yellow Factor 2: Label, Levels: gender specific vs. nonspecific.

Effect of drug dosage and sex on Alzheimer treatment. What are the Factors and levels?

Factor 1: drug dosage Levels: high vs Low Factor 2: sex Levels: male vs female This is a 2 x 2 Factorial ANOVA

Hypothesis testing with the Pearson correlation. State the hypotheses:

H0: ⍴ = 0 H1: ⍴ ≠ 0

Assumptions of one way ANOVA

Independence of observations within and between groups, one score should not influence others. Normality in the populations. Equal variances in the populations, homogeneity of variance.

Correlation

Measures and describes the relationship between two continuous variables.

The main effect of task modality: F(1, 150) = .06, p = .81. Retain or reject the null hypothesis with = .05?

Retain the null hypothesis

Choosing a test: when you have only two samples to compare

T-test or ANOVA, applies to both independent samples and repeated measures designs.

Assumptions for repeated measures t-test.

The observations with each condition must be independent. Within each condition, the scores are obtained from different individuals so should be independent of one another. The population of distribution of difference scores must be normal or relatively large n>30

Assumptions for an independent t-test

The observations with each sample must be independent. The populations from which the samples are selected must be normal. or Large sample sizes. The populations form which the samples are selected must have equal variances, homogeneity of variance.

Strength of the relationship

The range of the r value = [-1 +1] The less consistently scores on one variable change with scores on the other variable: —> r will become further from +/- 1.00 and closer to 0

2 x 3 factorial ANOVA, How many factors how many levels?

Two Factors, A and B. Factor A: 2 levels Factor B: 3 levels

2 x 2 factorial ANOVA, How many factors how many levels?

Two Factors, A and B. Factor A: 2 levels Factor B: 2 levels

One factor with multiple levels i.e. one independent or quasi-independent variable with multiple conditions we would use a one way ANOVA or a repeated measures ANOVA. What happens when there are 2 or more factors?

Use a Factorial ANOVA

To study the effects of physical discomfort on attention, Dr. Woods conducted the following study: A group of participants were required to keep one hand submerged in cold water. Hale of the participants kept their hands in the water for for four minutes. In addition, half of the participants were given a placebo pill and told it would reduce the pain of the water (pain relief assumed). The other half were given a placebo pill and told that it would have no effect (no pain relief assumed). While their hands were in the water, participants were asked to watch a video where a ball is quickly passed between and underneath three cups. At the end of the video, participants were asked to indicate under which cup the ball could be found. Whether or not the participant picked the correct cup was recorded (as a measure of whether they were paying attention). What is the statistical design? a) 2 x 2 b) 2 x 3 c) 2 x 4 d) 2 x 2 x 2

a) 2 x 2

Dr. Chang is curious as to whether exposing people to violent video games causes them to be more aggressive. She assigns half her participants to play a violent video game for 5 minutes and the other half to play the same game for 25 minutes. Afterward, she has them play a board game and has a well trained coder determine whether they are very aggressive in their playing style, barely aggressive, or not at all aggressive. To analyze his data, he can use: a) both an independent-samples t-test and a one way ANOVA b) both a repeated samples t test and a repeated measures ANOVA c) a one-way ANOVA d) a repeated measures ANOVA e) a factorial ANOVA

a) both an independent samples t-test and a one way ANOVA

Dr. Paruda tests whether people who eat sandwiches regularly are healthier than people who never eat sandwiches. To analyze her data she can use: a) both an independent samples t-test and a-one way ANOVA b) both a repeated samples t-test and repeated measures ANOVA c) a one-way ANOVA d) a repeated measures ANOVA e) a factorial ANOVA

a) both an independent-samples t-test and a one way ANOVA

Imagine that Dr. Woods decides to add another variable to his study. He is curious as to whether the results of the study vary based on pain sensitivity of the participants (low vs. medium vs. high). Which factorial notation would describe this new study? a) 2 x 2 x 2 b) 2 x 3 x 3 c) 2 x 2 x 3 d) 2 x 2 x 2 x 3

c) 2 x 2 x 3

Which of the following research situations would be most likely to use an independent measures design?a. Examine the development of vocabulary as a group of children mature from age 2 to age 3 b. Examine the long-term effectiveness of a stop-smoking treatment by interviewing subjects 2 months and 6 months after the treatment ends c. Compare the mathematics skills for 9th-grade boys versus 9th-grade girls

c. Compare the mathematics skills for 9th-grade boys versus 9th-grade girls

A health psychologist examines whether younger drinkers (30 years of age and younger) versus older drinkers (> 30 years of age) act sillier (i.e., more like they are drunk) when they drink alone, with one friend, with two friends, or with 4 friends. She randomly assigns 30 younger people and 30 older people to have two drinks (i.e., everyone has 2 drinks only) either alone, with one friend, with two friends, or with four friends. Different people are in each cell of the design. What is the statistical design? a) 2 x 2 x 3 b) 2 x 3 x 4 c) 2 x 3 d) 2 x 4

d) 2 x 4

Outliers

good practice: always report the presence of outliers. Many options; for example: - remove from analyses (but make sure to report!). report analyses both with and without outliers. "Winsorize": replace 10-25% of the tails of your data with the mean

In 1974, Loftus and Palmer conducted a classic study demonstrating how the language used to ask a question can influence eyewitness memory. In the study, college students watched a film of an automobile accident and then were asked questions about what they saw. One group was asked "About how fast were the cars going when they smashed into each other?" Another group was asked the same question except the verb was changed to "hit" instead of "smashed into."

independent samples t-test, one-way ANOVA

correlation coefficien

is a numerical value that describes 3 characteristics of the relationship between X and Y. 1 Form of the relationship. 2 Direction of the relationship. 3 Strength of the relationship.

Degrees of freedom for Factorial ANOVA

n-2

A psychologist is comparing the memory skills of elderly who live by themselves, who live with their families, and who live in a senior care facility

one-way ANOVA

The less tightly grouped the scores are (i.e. more dispersed)

r will become further from +/- 1.00 and closer to 0

Examples of Bivariate association studies

relationship between exercise and depression - link between parental language use and vocabulary development in 2 year-olds - association between number of sunny days and depressive symptoms Association is not equal to causation

Bivariate association studies

relationship between two measured variables

A developmental psychologist is examining the development of language skills from first grade to fourth grade, measuring the vocabulary of each child on a yearly basis

repeated-measures ANOVA

In a study by Stephens and colleagues (2009), each participant was asked to plunge a hand into icy water and keep it there as long as pain would allow. In one condition, the participants repeated their favorite curse words while their hands were in the water. In the other condition, the same participants repeated a neutral word.

repeated-measures t-test, . repeated-measures ANOVA

⍴ ("rho")

represents the true correlation of two variables in the population from which the sample was drawn

Correlation compares

scores on the first variable X to the scores on the second variable Y

r

the degree to which they vary

Curvilinear association

the increase in value of one variable is associated with both increases and decreases in the value of another variable. looks like rainbow.

Negative correlation:

the increase in value of one variable is associated with the decrease in the value of another variable

Positive correlation:

the increase in value of one variable is associated with the increase in the value of another variable

Factorial ANOVA Tests

whether two or more independent/quasi-independent factors relate to the dependent variable