## 09 Jun Research Methods in the Social Sciences

Running and Interpreting a t-Test Using Excel Due Date: Points: 100 Overview: For this assignment, you will apply your knowledge of experimental research to determine if there is a statistically significant difference between mean (average) outcomes for an experimental (Intervention group) group and a control group. You will run “descriptive statistics” and a “t-test” using a sample data scenario and set described below. The descriptive statistics will tell you means and standard deviations regarding the outcomes measured; the t-test will tell you if there is a statistically significant difference between the two means of the outcomes measured.

Instructions: In a hypothetical study, a researcher randomly assigned participants who had trouble dieting into one of two groups – an experimental (Intervention group) or a control group. In the experimental group, participants completed an intervention where were asked to think about how life would be better if they dieted and how life would be worse if they did not. Participants in the control group did not receive any sort of intervention. At the start of the study, all participants weighed 300 pounds. A month after the study began, participants were weighed again, and the number of pounds lost was recorded. The data collected is listed below. It was hypothesized that participants in the intervention group would lose more weight, on average, than participants in the control group.

Intervention Group (Weight Lost in Pounds)

Control Group (Weight Lost in Pounds)

20 2 21 1 17 0 18 2 21 0 22 0 16 3 17 1 20 0 16 2 14 4 17 1 22 0 16 3 17 2

PSY341–Research Methods in theSocial Sciences

Part A

For the data set above, determine the following:

1. The mean and standard deviation for weight lost in pounds for the intervention group. (20 points).

2. The mean and standard deviation for weight lost in pounds for the control group. (20 points).

Directions for Running Descriptive Statistics in Excel (Means and Standard Deviations): In the Resources section of the Unit, review the PowerPoint: “Running a t-Test in Excel”. This describes how to run both Descriptive Statistics and a t-test.

• Enter the Data Set Above into Excel • Click Data • Click Data Analysis • Click Descriptive Statistics • Input Range (Select Data Columns) • Check Summary Statistics • Click OK

Part B

3. Run a t-test and determine the t statistic. (20 points).

4. Was there a statistically significant difference in mean scores for weight lost in pounds between the intervention group and the control group? How can you tell? Look at the p value for assistance. Explain your answer. (20 points).

Directions for Running a t-Test in Excel • Click DataClick Data Analysis • Click t-test (assuming equal variance) • Indicate Variable 1 Range • Indicate Variable 2 Range • Enter .05 as your alpha level • Click OK

Part C

5. Create a bar graph of the means for weight lost in pounds for both the intervention group and the control group. Add a title and label your axes. (20 points).

Directions for Creating a Bar Graph in Excel Refer to the video under Readings and Resources in Unit 6, entitled, “Column Graphs and t-test in Excel” for help in creating a bar graph using Excel. You may also refer to the “Creating a Bar Graph in Excel” PowerPoint under the Unit 6 Readings and Resources. Requirements:

• Answer all questions in Part A, B, and C. • Submit a Word document with your answers.

Be sure to read the criteria below by which your work will be evaluated before you write and again after you write.

Evaluation Rubric for t-Test Assignment

CRITERIA Deficient Needs Improvement

Proficient Exemplary

0 points 20 points Mean and Standard Deviation for Weight Lost in Pounds for the Intervention Group

The mean and standard deviation are not provided or are inaccurate.

The mean and standard deviation are provided and accurate.

0 points 20 points Mean and Standard Deviation for Weight Lost in Pounds for the Control Group

The mean and standard deviation are not provided or are inaccurate.

The mean and standard deviation are provided and accurate.

0 points 20 points T-Test The result of the t-

test (t statistic) is not provided or is inaccurate.

The result of the t-test (t statistic) is provided and is accurate.

0 – 14 points 15 – 16 points 17 – 19 points 20 points Statistical Significance

Either a statement is not made as to whether the difference in means scores is statistically significant and/or an explanation is not given as to why the difference is statistically significant or not, or the statement and explanation given are incorrect.

Statement is made as to whether the difference in means is statistically significant, but no explanation is given as to why the difference is statistically significant or not.

Statement is made as to whether the difference in means is statistically significant, but the explanation is lacking detail.

Statement is made as to whether the difference in means is statistically significant and a thorough and accurate explanation is given as to why the difference is statistically significant or not.

0 points 1 – 11 points 12 – 19 points 20 points Bar Graph of Mean Scores for the Intervention Group and the Control Group

Graph of mean scores is not provided.

Graph is provided but does not accurately illustrate the difference in means scores between each group. Graph title and axes

Graph is provided and accurately illustrates the difference in means scores between each group. Graph is missing some

Graph of means is provided and accurately illustrates the difference in mean scores between each group. Graph includes

CRITERIA Deficient Needs Improvement

Proficient Exemplary

are provided but mislabeled.

important components, such as a title or labeled axes.

a title and labeled axes.

Overview:

Instructions:

Directions for Running a t-Test in Excel

Directions for Creating a Bar Graph in Excel

Requirements:

Evaluation Rubric for t-Test Assignment