Statistical Analysis using Independent Samples t-test

This very common method of statistical analysis allows us to test the difference between two independent means. In layman’s terms, this means we are looking for differences between two groups of participants that are not related. In statistical terms, this means that the scores of the two groups are not correlated.

How is the independent samples t­-test used?

The independent samples t-test can be used when looking for differences between any two groups on a single measure, e.g. differences on SAT scores by gender, differences on GPA by gender, or differences on ACT scores by ethnicity (African American vs. Caucasian).

What types of variables can be used in an independent samples t-test?

There are two variables in an independent samples t-test, an independent variable and a dependent variable. The independent variable is the grouping variable and must be dichotomous or two groups. The dependent variable must be continuous/interval, however, sometimes it’s okay to use ordinal variables, but that is a whole other topic.

What are typical uses of the independent samples t-test?

Often, independent samples t-test are used to look for differences between control and experimental groups. Some research designs employ both an experimental group and a control group with measures before a treatment and after a treatment for both groups. While the statistical test for examining differences within the control group before and after the treatment and within the experimental group before and after the treatment is a dependent samples t-test, the statistical test for examining differences between the control group and the experimental before the treatment and then again after the treatment is an independent samples t-test.

If I am a researcher hoping that my additional math class as a treatment is effective, I am hoping to find that the control and experimental groups are the same pre-treatment, but different post-treatment. Hopefully, my experimental group would have higher math scores post treatment, than my control group. For information on conducting the independent samples t-test in SPSS, please see the information on www.

Statistical Analysis

How do I know what type of statistical analysis to conduct?

Researchers working on studies, theses, and dissertations, often ask this question. Ideally this is a question to ask at the beginning of the research project, rather than the end. It is at this point that research needs should be assessed and hypotheses determined. During the initial stages of planning is the time to involve a statistics consulting firm to help you formulate the basis of your study. There are many things that can influence the type of statistical analysis to use but here are a few important ones:

1. Empirical information (statistical analysis) related to your study

If you are at the point in your study or dissertation that you have begun to consider the type of statistical analysis you need to conduct, then hopefully you have considered the statistical analysis of other researchers in similar studies. It is wise to do this, if only for comparison purposes. However, utilizing the same statistical analysis that has been utilized by other researchers and experts in your field will lend credence to your findings and avoid the difficult, if not embarrassing, task of defending why you chose a different type of statistical analysis.

2. University/College requirements

While I don’t believe it appropriate, many colleges and universities stipulate the type of statistical analysis their dissertation candidates can use. Often, the statistical analysis requirement is the use of multivariate analysis. Make sure you are aware of any of these requirements prior to formulating your research questions and hypothesis.

3. Formulation of the research questions and hypothesis

It is very important to have an idea of the statistical analysis to be used before formulating your research questions, hypothesis, and methodology. The wording of your research questions and hypothesis will determine the type of statistical analysis to be conducted.

· Words like relationship and correlation, tend to correspond with correlational statistical analysis. Sometimes these words also represent regression statistical analysis, but usually correlational statistical analysis.

· Words like predict, affect, and impact tend to correspond with regression statistical analysis, both linear regression and logistic regression.

· Research questions using the difference tend to correspond with t-­tests, both dependent and independent and ANOVAs.

This means you should have an idea of the statistical analysis to be used before crafting your research questions and hypothesis. It is much easier to do this before the proposal is approved than after.

4. Ability of the researcher

While every researcher aspires to change the world, the statistical analysis should fit within the comfort and abilities of the researcher. If you are having difficulty formulating your methodology around statistical analysis with which you are comfortable, it may be wise to consult a statistics consulting firm to help you with the data analysis and statistical analysis. If you have had two or three statistics classes three years ago, you may not want to choose a complex statistical analysis utilizing structural equation modeling or even multivariate analysis. Though a statistics consulting firm will help tremendously in explaining and using complex analysis, you are ultimately the one that will be defending it and explaining it to your committee. Just a reminder, a wise person knows their limitations.

For a customized, confidential help formulating your research questions and hypothesis, and/or conducting your statistical analysis, please call Statistics Solutions Inc. (877) 437-8622 for a free 30 minute consultation .

Where can I find Dissertation Assistance?

Most students secure dissertation assistance in the dissertation process. Let’s face it, the dissertation is new terrain. Statistics Solutions are professional researchers and statisticians providing dissertation assistance in this new terrain. Most students need dissertation assistance with their method section—refining their research questions, selecting the correct data analysis plan, and justifying the sample size.

When you write your research questions, make sure each of the variables in your research questions can be measured, and use language in your questions that relates to the heart of what you want to know. For example, are you looking to examine differences on SAT scores by gender? If so, a t-test is the appropriate statistic to examine differences. Or are you seeking to predict SAT scores from gender? Here a linear regression would be the correct statistical test. You can see that the phrasing of the research question drives the type of analysis: this is the type of dissertation assistance that Statistics Solutions provides.

Frequently, justifying the sample size is dissertation assistance that students look for. Just like the phrasing of the research question drives the statistical test, the statistical test drives how many participants are necessary. Statistics Solutions frequently assists dissertation students daily with sample calculations and sample size equations.

When you get dissertation assistance, get assistance from individuals that have actually completed a dissertation! It only makes sense to get dissertation assistance from those who have personally traveled the dissertation path themselves.

If you have questions and need dissertation assistance, feel free to contact Statistics Solutions for a free 30-min consult. Our phone number is (877) 437-8622, or email us at: www.StatisticsSolutions.com.

Get the dissertation assistance that you need and the very best in finishing your dissertation!