How many treatment means are there in a two-factor experiment?
In a two-factor experiment with 2 levels of factor A and 2 levels of factor B, three of the treatment means are essentially identical and one is substantially different from the others. What result (s) would be produced by this pattern of treatment means?
How many scores are obtained in each treatment condition?
A between-subjects experiment comparing four treatment conditions produces 20 scores in each treatment condition. How many scores were obtained for each participant? A between-subjects experiment comparing four treatment conditions produces 20 scores in each treatment condition.
How to evaluate the mean differences among three treatment conditions?
An analysis of variance is used to evaluate the mean differences among three treat- ment conditions. The analysis produces SSwithin treatments 5 20, SSbetween treatments 5 40, and SStotal 5 60.
What is Kelley's experiment in introductory psychology?
In Kelley's (1950) classic study of the effects of people's expectations on their impressions of others, he gave Introductory Psychology students written descriptions of a guest lecturer before he came to class. Kelley handed out the descriptions at random.
What is AN experiment with one independent variable?
When a research design is a “one-way” design, it involves only one independent variable. When a research design is an “independent samples” design, random assignment is used to place participants into comparison groups.
When there is a statistically significant difference between two treatment groups we know that quizlet?
When a difference between two groups is statistically significant, this means that... the difference is not likely to have occurred on its own, without the benefit of the independent variable.
Why do researchers conduct post hoc comparisons after a significant F ratio quizlet?
The purpose of post hoc tests is to determine exactly which treatment conditions are significantly different. A test that uses an F-ratio to evaluate the significance of the difference between any two treatment conditions.
Which of the following are factors that can contribute to a null effect in a study?
Null effects can be caused by excessive amounts of unsystematic variance, or noise. This within-group variance can be caused by a dependent variable with poor reliability or in which insufficient data is collected.
When there is a statistically significant difference between two treatment groups we know?
The determination of whether there is a statistically significant difference between the two means is reported as a p-value. Typically, if the p-value is below a certain level (usually 0.05), the conclusion is that there is a difference between the two group means.
What is the 5 level of significance?
The level of significance is taken at 0.05 or 5%. When the p-value is low, it means that the recognised values are significantly different from the population value that was hypothesised in the beginning. The p-value is said to be more significant if it is as low as possible.
When comparing more than two conditions should you use an analysis of variance rather than using several t tests and if so why?
there are no differences between any of the population means. When comparing more than two treatment means, why should you use an analysis of variance instead of using several uncorrected t tests? Conducting several t tests would inflate the risk of a Type I error.
Why do researchers have to conduct post hoc comparisons after a significant F ratio?
Post hoc tests allow researchers to locate those specific differences and are calculated only if the omnibus F test is significant. If the overall F test is nonsignificant, then there is no need for the researcher to explore for any specific differences.
How many F ratios does a two way Anova have?
Unlike a one-way ANOVA, a two-way ANOVA presents 2 F statistics. This test statistic summarizes whether there is a...
How many variables at a time can be changed in an experiment?
Testing only one variable at a time lets you analyze the results of your experiment to see how much a single change affected the result. If you're testing two variables at a time, you won't be able to tell which variable was responsible for the result.
Which is a question that researchers may ask when deciding how do you control confounding variables?
Which is a question that researchers may ask when deciding how to control confounding variables? What factors, other than the independent variable, could affect the outcome? An important function of a research design in a quantitative study is to exert control over which variables?
What causes a null result?
In statistical hypothesis testing, a null result occurs when an experimental result is not significantly different from what is to be expected under the null hypothesis; its probability (under the null hypothesis) does not exceed the significance level, i.e., the threshold set prior to testing for rejection of the null ...
What is the purpose of Dr. Pritts' experiment?
The hormone level is a factor in the experiment. Dr. Pritts is trying to determine whether elevated levels of a particular hormone alter rats' spatial ability. She injects rats either with the hormone or a saline solution, then times how long it takes them to find the hidden platform in a Morris Water Maze.
Why do researchers select extreme values of an independent variable?
extreme values increase the possibility of detecting a change across conditions. Researchers often select extreme values of an independent variable because. external validity.
What did Kelley study?
In Kelley's (1950) classic study of the effects of people's expectations on their impressions of others, he gave Introductory Psychology students written descriptions of a guest lecturer before he came to class. Kelley handed out the descriptions at random. Half the students were told the visitor was a "warm" person and half were told he was ...
Should you ask your friends to participate in your study?
You shouldn't ask your friends to participate in your study because they may. 100 participants. If a between-subjects experiment produces 50 scores in treatment 1 and 50 scores in treatment 2, then the experiment must have employed. levels. An independent variable always has at least two.
What is the significance level of a hypothesis test?
For example, hypothesis tests with a significance level of 0.05 correspond to 95% confidence intervals.
What is an omnibus test?
Statisticians refer to the ANOVA F-test as an omnibus test. Welch’s ANOVA is another type of omnibus test. An omnibus test provides overall results for your data.
Does the omnibus ANOVA test identify specific group differences?
In this blog post, you’ve seen how the omnibus ANOVA test determines whether means are different in general, but it does not identify specific group differences that are statistically significant.
Do experiment-wise and family-wise tell you what group means?
Yes, they tell you which group means are significantly different from other group means. Crucially, they also control the experiment-wise, or familywise, error rate. In this context, experiment-wise, family-wise, and family error rates are all synonyms that I’ll use interchangeably.
Do you need to compare all groups in a post hoc study?
However, depending on your study’s purpose, you might not need to compare all possible groups. Your study might need to compare only a subset of all possible comparisons for a variety of reasons. I’ll cover two common reasons and show you which post hoc tests you can use.