Analysis - Comparing group means
Background and objectives - The balance_FALL17.xlsx dataset represents data from a fictitious study that explores the impact of two different interventions designed to help elderly clients living at home to improve balance. The idea is that clients with less environmental risks and with better balance would have less fear of falling. Patients completed several scales and then were randomly assigned to one of two groups: sessions designed to promote flexibility (stretching) or sessions designed to increase endurance (strengthening). Instrumental Activities of Daily Living (IADL) were also collected at admission with lower scores implying less independence.
The intent of this analysis is to have you use these data to demonstrate your ability to:
1) Identify the appropriate statistical tests to test differences in means;
2) Conduct Excel analyses to test for statistical differences; and
3) Summarize findings as you would in a journal article or report.
Assignment -
Part 1: Describe the sample characteristics and baseline values, comparing the two groups' characteristics.
With any analysis, the first step is to examine your data, assessing the degree of missing data, the potential miscodes, and conducting a descriptive analysis. Then, a table is created to describe the sample characteristics. Since this is an intervention study with two groups (flexibility or endurance), the characteristics of the 2 groups should be described separately, rather than report on the entire sample. The example table shell below gives you an illustration of how this might look. Using Excel, calculate the descriptive statistics for gender, age, the baseline environmental risk, IADL score and balance. Then describe the findings in the table.
Part 2: Comparing two independent group means
In an intervention it is always good to examine if the groups are comparable at the start, so the alternative hypothesis is:
The two groups (flexibility or endurance) will differ in their balance score at time 1.
For your write up, follow the steps of hypothesis testing, stating the null hypothesis, review assumptions (show evidence you explored if the assumptions were met), and consider if the hypothesis is directional or not. Consider if the distribution of balance scores is approximately normal. You do not need to statistically test for homogeneity of variance in Excel but you should consider (calculate and 'eye ball compare') if the standard deviations of the groups being compared are similar (hint: know how SD relates to variation) so you can select the proper t-test condition to run. Write a few sentences describing your steps and the results of the testing, making sure that you note what group means are being compared and what the results would mean to someone who does not understand statistics. Include a copy of your EXCEL output.
Part 3: Comparing means of a single group, pretest-posttest
After the interventions do we see any change overall in balance scores regardless of any group assignment? For the entire sample (regardless of the intervention), test the hypothesis:
Having either of the interventions (flexibility or endurance) will change one's balance score (i.e., compare Time 1 to Time 2).
Again for your write up, follow the steps of hypothesis testing, stating the null hypothesis, review assumptions, and consider if the hypothesis is directional or not. Make sure that you evaluate the assumptions for the statistical test, particularly the level of the measurement and the normality of the distribution (show evidence). Write a few sentences describing your steps and the results of the testing, making sure that you note what group means are being compared and what the results would mean to someone who does not understand statistics. See the end of the assignment for examples of how to write up the results. Include a copy of your EXCEL output.
Part 4: Comparing means of more than 2 groups
IADL at admission may influence the fear of falling. A variable has been created reflecting low, medium and high IADL at baseline. Test the following hypothesis:
Fear of falling is statistically different across the three levels of baseline IADL (low, medium, and high).
As with the t-tests, assumptions of the statistical tests must be considered. You do not need to test for homogeneity of variance in Excel but you should consider if the standard deviations of the 3 groups being compared are similar. Write a few sentences describing your steps and the results of the testing, making sure that you note what group means are being compared and what the results would mean to someone who does not understand statistics. Include a copy of your EXCEL output. If the ANOVA F test is significant, further post hoc testing would be needed to compare which means are statistically different (e.g., Group 1 vs 2? Group 1 vs 3? Group 2 vs. 3?). This video shows how to do this but it is not required for this assignment.
Attachment:- Assignment Files.rar