BME100 f2014:Group22 L1

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BME 100 Fall 2014 Home
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- Independent and Dependent Variables 
- Experimental and Control groups
- Randomization
- Sample size
- Bias
- T-test and ANOVA
- Pearson's R
- Power Analysis

Mini-problem: This semester, you and your team are assisting a graduate student, Kristen, in a research lab. You are studying the effects of inflammation, but the lab is short on cash. You must determine the lowest possible dose of an inflammation inducing agent (lipopolysaccharide) to increase a newly discovered inflammatory protein (Inflammotin) in the elderly. The protein is measured in blood samples using ELISA. Prior work has shown that 10mg pill of lipopolysaccharide can increase protein levels so this is a good starting point.


1. What are your independent and dependent variables? 
2. Describe your experimental design. 
a. How many groups? 
b. How many subjects/group?
3. How will you select your subjects?
4. What are some of the potential sources of error or biases that could affect your results and how would you control for them?

Independent and Dependent Variables

Independent: Dosage of lipopolysaccharide, because the dosage is what is being changed to determine the lowest effective dose.

Dependent: Levels of inflammatin, because this is what is changing as a result of the medication and what is being measured to determine the actual effectiveness of the dose of LPS.

Experimental Design


We will select our participants by visiting a retirement home and assigning each resident a number. a. There will be four groups in total. We are low on money, so the experimental groups will be: a group receiving a placebo (0mg of LPS), a group receiving a dose of 7.5mg of LPS, a group receiving a dose of 5mg, and a group receiving 2.5mg. We will not be testing 10 mg because we know that 10mg is an effective dose, so to save money we will not retest this dose. We are looking for the lowest effective dose, so we are only checking for lower than 10mg.


The subjects selected will be ages 65 and up.

Number of subjects per group

There will be 20 subjects in each group(80 total subjects in experiment) so that there is a large sample size without going over budget. There will be 4 different groups receiving different doses as mentioned above.

Subject Selection

To select our subjects we will be using a random number generator we will select 20 of the elderly residents to each group. If the random number generator generates a number not assigned to a resident or that is already selected, we will generate another random number. This randomization of subject selection should alleviate experimental bias in the choice of subjects, because no certain subjects will be favored. This should allow the data collected to accurately represent the effects of lipopolysaccharide on people.

Sources of Error and Bias

There could be several sources of error including: subjects being allergic to the drug, sample sizes too small to have a measurable effect therefore making a falsely negative test, or the placebo effect where the subjects given the placebo drug show a change in inflammation. Additionally, human error though experimenter bias can effect the results so to control this, it should be performed as a double blind experiment where neither the experimenters nor the subjects know the dosage of drug being given to them. If a wide enough group of subjects is selected then if a subject has a reaction to the drug that differs from others, there are enough other participants in the study to still have accurate results. If the sample sizes are too small of a dose difference to have a measurable effect, then a new experiment could be designed on a wider and larger group of subjects.