Purchase Solution

ANOVA conclusions and posthoc tests

Not what you're looking for?

Ask Custom Question

Graduate Level: Please answer the question and provide an example. Thanks.

Purchase this Solution
Solution Preview

If you have a significant difference (ie. a main effect of treatment) but more than two treatment groups, all you know is that there is a significant difference somewhere between your groups. You do not yet know where that difference is coming from.
Let's look at an example.
Imagine you're comparing doctors, lawyers, and nurses on their ability to diagnose various diseases. Each group is given 30 'medical cases' and asked to provide a diagnosis for each case. Your dependent variable can be the number of cases correctly identified. Let's say the mean number correct for each group is as follows:

Doctors: 27
Nurses: 25
Lawyers: 13

Now, if we were to run an ANOVA on this, our null hypothesis would be:
mean_doctors=mean_nurses=mean_lawyers
and our alternative hypothesis would be that one or more of these equalities is incorrect. The important thing to remember is this: ONE OR MORE IS INCORRECT. So if we get a significant p-value for this ANOVA, we only know that:
maybe doctors and nurses and lawyers are all different from one another
OR maybe doctors differ from nurses but not from lawyers
OR maybe doctors differ from lawyers but ...

Purchase this Solution
Free BrainMass Quizzes
Measures of Central Tendency

Tests knowledge of the three main measures of central tendency, including some simple calculation questions.

Terms and Definitions for Statistics

This quiz covers basic terms and definitions of statistics.

Measures of Central Tendency

This quiz evaluates the students understanding of the measures of central tendency seen in statistics. This quiz is specifically designed to incorporate the measures of central tendency as they relate to psychological research.

Know Your Statistical Concepts

Each question is a choice-summary multiple choice question that presents you with a statistical concept and then 4 numbered statements. You must decide which (if any) of the numbered statements is/are true as they relate to the statistical concept.

View More Free Quizzes
Related BrainMass Solutions

  • ANOVA and Hartley's test

    So the short answer is that as long as you use appropriate posthoc corrections following an ANOVA, your chance of making a Type I error will be lower for that analysis than for multiple t-tests. 2.

  • Independent samples and ANOVA

    Posthoc tests allow you to break down the significant F to investigate which groups differ from one another. You can use ANOVA if you have an independent variable with at least 3 levels and a continuous dependent variable.

  • SPSS Analysis

    In addition, you need to comment on the results of different tests that were done, and if they lead to the same or different conclusions and why. Please paste everything in a word file and send the spss file also.

  • Analysis of variance in SPSS

    All you have to do is do the following three tests: t test, and determine if pooled variance can be used. Anova test and one related sample t test. For anova make sure you use tukey cramer to see which population is different from the other 2.

  • Parametric vs. Non-parametric Testing

    (C) Should the conclusions between the two tests consistent? Why or why not? If the conclusions are not consistent, which one would you agree with and why? The problem is solved using One-way ANOVA and KRUSKAL WALLIS TEST.

  • Single Factor ANOVAs

    Because we did not get a significant p-value, do not need to do post-hoc tests. Conclusions: The ANOVA had a high p-value, indicating that the means are not significantly different from one another.

  • Two-Way ANOVAs: Interpret the results from the sex X treatment.

    Since there are three treatments, we don't know where that difference is (1 could be better than 2 and 3, or 3 could be better than 2, which is better than 1, and so on) and we'd need to do posthoc tests to figure that out.

  • Research using statistical tests

    73871 Research using statistical tests Select an article that describes research using one or more statistical tests (z, t, ANOVA, chi square, regression) as part of the data analysis.

  • ANOVA example

    There are several possibilities you can choose from - think about what might make sense (and why) and choose that as your outcome. Since you have 3 groups, you'll have to use ANOVA. T-tests can only handle up to 2 groups.

  • ANOVA and Significance Levels

    And what are some conclusions you might draw from that? Just like you would use a z-test or a t-test to see if two groups have significantly different means, you would use ANOVA to compare the means of three or more groups.

View More Related Solutions