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### Not Ready for Human Consumption: Doing Preclinical Studies

Before any proposed treatment can be tested on humans, there must be at least *some* reason to believe that the treatment might work and that it won't put the subjects at undue risk. So every promising chemical [more…]

### Human Drug Testing Phase I: Determining the Maximum Tolerated Dose

The first step (Phase I) in human drug testing is to determine how much drug you can safely give to a person, which scientists express in more-precisely defined terms: [more…]

### Human Drug Testing Phase II: Finding Out About the Drug's Performance

After the Phase I trials of human drug testing, you'll have a good estimate of the maximum tolerated dose (MTD) for the drug. The next step is to find out about the drug's safety and efficacy at various [more…]

### Human Drug Testing Phase III: Proving That the Drug Works

If Phase II of human drug testing is successful, it means you've found one or two doses for which the drug appears to be safe and effective. Now you take those doses into the final stage of drug testing [more…]

### What Are Bioequivalence Studies?

A *bioequivalence study* is usually a fairly simple pharmacokinetic study, having either a parallel or a crossover design. You may be making a generic drug to compete with a brand-name drug already on the [more…]

### How to Create a Data Dictionary to Describe Your Biostatistics Data

Every research database, large or small, simple or complicated, should be accompanied by a *data dictionary* that describes the variables contained in the database. It will be invaluable if the person who [more…]

### How to Put Together a Protocol for a Clinical Study

A *protocol* is a document that lays out exactly what you plan to do in a clinical study. Ideally, every study involving human subjects should have a protocol. [more…]

### Protecting Clinical Study Subjects

After you've designed your study and have described it in the protocol document, it's time to set things in motion. In any research involving human subjects, two issues are of utmost importance: [more…]

### Collecting and Validating Clinical Study Data

If the case report form (CRF) has been carefully and logically designed, entering each subject's data in the right place on the CRF should be straightforward. Then you need to get this data into a computer [more…]

### Human Drug Testing Phase IV: Keeping an Eye on the Marketed Drug

Being able to market the drug doesn't mean you're out of the woods yet! During a drug's development, you've probably given the drug to hundreds or thousands of subjects, and no serious safety concerns [more…]

### Thorough QT (Interval) Studies in Biostatistics

In the mid-1900s it was recognized that certain drugs interfered with the ability of the heart to "recharge" its muscles between beats, which could lead to a particularly life-threatening form of cardiac [more…]

### Levels of Measurement for Biostatistics Data

Around the middle of the 20th century, the idea of *levels of measurement* caught the attention of biological and social-science researchers, and, in particular, psychologists. One classification scheme, [more…]

### How to Collect Categorical Data in Biostatistics

Setting up your data collection forms and database tables for categorical data requires more thought than you may expect. Everyone assumes he knows how to record and enter categorical data — you just type [more…]

### How to Record Numerical Data for Biostatistics

For numerical data, the main question is how much precision to record. Recording a numerical variable to as many decimal places as you have available is usually best. [more…]

### How to Enter Date and Time Data for Biostatistics

When you enter numerical data into your computer, *don**'**t* combine two numbers into a single variable (such as 145/85 for systolic and diastolic blood pressure). When it comes to dates and times, however, [more…]

### How to Summarize and Graph Categorical Data

A categorical variable is summarized in a fairly straightforward way. You just tally the number of subjects in each category and express this number as a count — and perhaps also as a percentage of the [more…]

### Other "Means" (besides the Arithmetic Mean) to Measure Central Tendency

Several other kinds of means, besides arithmetic, are useful measures of central tendency in certain circumstances. They're called *means* because they all involve the same [more…]

### Standard Deviation, Variance, and Coefficient of Variation of Biostatistics Data

The *standard deviation* (usually abbreviated *SD,**sd,* or just *s*) of a bunch of numbers tells you how much the individual numbers tend to differ (in either direction) from the mean. It's calculated as follows [more…]

### The Range of a Set of Numbers

The *range* of a set of values in your data is the difference between the smallest value (the *minimum* value) and the largest value (the *maximum* value):

Range [more…]

### Sample Statistics and Population Parameters

Scientists conduct experiments on limited *samples* of subjects in order to draw conclusions that (they hope) are valid for a large *population* of people. Suppose you want to conduct an experiment to determine [more…]

### Accuracy and Precision in Terms of the Sampling Distribution

The idea of a sampling distribution is at the heart of the concepts of *accuracy* and *prec**i**sion*. Imagine a scenario in which an experiment (like a clinical trial or a survey) is carried out over and over [more…]

### How to Get More Accurate Measurements in Your Data

Measurement accuracy very often becomes a matter of properly calibrating an instrument against known standards. The instrument may be as simple as a ruler or as complicated as a million-dollar analyzer [more…]

### How to Improve Sampling Precision

You improve the precision of anything you observe from your sample of subjects by having a larger sample. The *central limit theorem* (or CLT, one of the foundations of probability theory) describes how [more…]

### Comparing Averages: How Situational Differences Determine Test Methods

You may wonder why there are so many tests for such a simple task as comparing averages. Well, "comparing averages" doesn't refer to a single task; it's a broad term that can apply to a lot of situations [more…]

### How to Use Student t Tests to Compare Averages

You can run the Student t tests using typical statistical software and interpret the output produced. In this example, you'll be using the software package OpenStat. [more…]