Statistics and research method
1) Explain the difference between a RMANOVA and a-test. When are each used when analyzing statistics
2) Develop a research question and corresponding hypothesis for a clinical trial investigating the effect of resveratrol on health and chronic disease. You can select the population and outcome variables. Identify independent and dependent variables. What statistical procedure would you use to analyze your data and why?
3) Explain why sample size calculations are used. Does a cross-over design effect sample size calculations compared to studying two homogenous groups?
4) If studying two homogenous groups, how do you determine if they are homogenous? If they are not homogenous, what statistical procedure needs to be followed when analyzing the results of a research project?
5) If recruiting participants for a study, how do you assure groups are homogenous prior to initiating the study?
6) The following excerpt is from a research article. The purpose, study design, statistics are provided as well as two figures of the results. Based on the purpose and study design, are the correct statistical procedures performed. Explain why or why not.
The purpose of this study was to examine the effect of a moderate dose of ibuprofen (400 mg/d) consumed on a daily basis after resistance training on muscle hypertrophy and strength. A secondary purpose of our study was to examine whether ingesting ibuprofen after exercise has any effect on perceived ratings of muscle soreness. Our hypothesis was that chronic consumption of ibuprofen would lead to decreased muscle hypertrophy, strength, and muscle soreness compared to placebo.
A counter-balanced double-blinded design was used where subjects were randomly assigned to ingest ibuprofen (two 200mg tablets/ day) immediately after training the biceps of one arm and placebo after training the other arm the next day. The counter balancing ensured that the number of subjects receiving ibuprofen after training their dominant arm was equal to the number who received ibuprofen after training their non-dominant arm. Peak plasma concentration of ibuprofen is reached about 1-4 hours after ingestion (Davies 1998), which corresponds to the time at which muscle protein synthesis is significantly elevated after biceps exercise (Chesley et al. 1992; MacDougall et al. 1995). The active moiety of ibuprofen is virtually entirely excreted within 24 hours following administration (Davies 1998); therefore, the ibuprofen would have negligible effect on the arm, which received the placebo. Subjects trained 5 days per week for 6 weeks; therefore, each arm was trained over 15 exercise sessions. Muscle thickness and strength were determined before and after the 6 weeks of training and muscle soreness was evaluated everyday during the training program.
All data are reported as mean ± SE. T-tests were performed on baseline data to determine if groups were the same at baseline. T-tests were also performed to determine the effect of ibuprofen on training adaptations and to determine if ibuprofen arm’s response was different from the control arm’s. All data were analyzed using Statistica 7.0 (StatSoft, Tulsa, OK). Significant was set at p<0.05.
Figure 1. Changes in strength over time for the ibuprofen and placebo arms. *Indicates significantly different from Pre.
Figure 2. Ratings of perceived muscle soreness as a function of weeks of training. *Indicates significantly different from week 1.
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