A researcher is studying the effects of sex—male and female—and dietary sugar on energy level. Male and female participants agree to follow either a high sugar or low sugar diet for eight weeks. The researcher asks the participants to finish a number of questionnaires, including one assessing energy level, before and after the program. The researcher is interested in determining whether a high or low sugar diet affects reported energy levels differently for men and women. At the end of the program, the researcher examines scores on the energy level scale for the following groups: Men - low sugar diet; Men - high sugar diet; Women - low sugar diet; Women - high sugar diet. What statistic could the researcher use to assess the data? What criteria did you use to determine the appropriate statistical test?

What statistic could the researcher use to assess the data? 

Answer: Analysis of Variance (ANOVA)

What criteria did you use to determine the appropriate statistical test?

a. Number of groups being compared in this research study. 

b. Correct identification of dependent and independent variables of this research study. 

Kindly see the explanations below. Thank you. 

Disclaimer: This is my own analysis as a licensed medical doctor who has a premedical degree in Behavioral Sciences. All information that I shared were based on my own experience as a researcher and a doctor. Thank you. 

Step-by-step explanation

What statistic could the researcher use to assess the data? 

Answer: Analysis of Variance (ANOVA)

Analysis of Variance, also called ANOVA, is an excellent statistical test to assess the data of this study. First, ANOVA is an effective choice to help you analyze three or more groups. In this study, you have four (4) groups to compare and analyze: 

Group 1 : Men - low sugar diet

Group 2: Men - high sugar diet

Group 3: Women - low sugar diet

Group 4: Women - high sugar diet

These 4 groups are to be compared effectively when you choose ANOVA. For research analysis in the field of psychology and social sciences, we usually use the latest version of the software SPSS (Statistical Package for the Social Sciences). You can input the data of these 4 groups in SPSS and simply choose and click "ANOVA" to help you analyze these group of people. The values will appear and will usually show how the relationship of each group work. The hypothesis of this study can only be confirmed (or rejected) if each group is analyzed best by using ANOVA as the statistical test. 

What criteria did you use to determine the appropriate statistical test?

a. Number of groups being compared in this research study. 

The number of groups being compared in this study is 4 groups. These 4 groups cannot be analyzed using only simple statistical tests such as T-test or Pearson. What you need is a more advanced and sophisticated statistical test such as that of ANOVA. This test encompasses comparison of at least 3 or more groups and analyzing the relationship of each other with respect to the p-value and confidence interval that you have set for this study. Usually, for a psychology or a social science research, a p-value of <0.05 is deemed to be acceptable already. If the desired p-value is achieved, this signifies that there is a relationship between the variables that you are trying to understand in a research study. 

b. Correct identification of dependent and independent variables of this research study. 

This is important to determine the appropriate statistical test. The independent variables of this study are (1) sex (men or women), (2) level of sugar diet (high sugar or low sugar diet). In contrast, the dependent variable (also called as the outcome variable) of this study is the "energy level of male and female participants." Since you have correctly identified the independent and dependent variables of this study, it is now much easier to analyze what statistical test is the most appropriate for this study. Given that these are your variables, you will come up with 4 groups for this study (Group 1 : Men - low sugar diet; Group 2: Men - high sugar diet; Group 3: Women - low sugar diet; Group 4: Women - high sugar diet). Since you have generated 4 groups, your goal now is to know the outcome or dependent variable - i.e. the energy level. So in order to know this, it is good to compare these groups using the statistical test ANOVA. This statistical test compares three or more groups which is deemed very suitable for this research study.