The Basic Principles of Biostatistics

Biostatistics is the application of statistics to problems in medicine, biology, and public health. The principles of biostatistics include characterization of population, estimation of magnitude of problem, and comparisons between groups of subjects. Using these principles, researchers can improve their methods, save time, and improve the outcomes of medical research. For instance, the use of biostatistics to predict health outcomes can help identify trends and detect problems early.

P VALUE

The use of p-values in biostatistics is a widely used statistical term. It helps researchers determine the significance of a study based on statistical methods such as likelihood ratios and the area under the receiver operator characteristic curve. A p-value is an important statistical term in biomedical research because most researchers base their decisions on the probability p. However, the use of this statistic can be a source of serious methodological error, and it is necessary to understand how to interpret it correctly.

In biostatistics, the P-value measures the statistical significance of observational data. Researchers may find a correlation between two variables, but the relationship may be a coincidence. The p-value calculation helps them to determine whether the observed relationship is real or just a coincidence. Earlier versions of this article incorrectly described the definition of p-value as the probability that the results would have been obtained through random chance.

Hypothesis testing

To conduct a study, a researcher must test a hypothesis. Typically, he can compare two groups by using the Fisher test and the Neyman-Pearson test. The Fisher test is analogous to a true/false question; while the Neyman-Pearson test is analogous to a multiple choice question. Both tests use similar statistics to test whether the results of two groups are significant. For instance, a study comparing the rate of intubation of a pediatric group to a control group would use the Fisher test.

The first step in the hypothesis testing process is establishing the null hypothesis. The null hypothesis is the statement that the study will find no difference between two variables. A null hypothesis (H0) states that no relation exists between two variables and that any effect of one variable on the other is purely due to chance. The null hypothesis is as important as the alternative hypothesis. The null hypothesis must satisfy the necessary conditions to conduct a test.

Multicollinearity

A multicollinearity problem occurs when the independent variables are highly correlated, meaning they cannot be separated by their effect on the outcome variable. This type of multicollinearity is often caused by poor experimental designs, 100% observational data, or other methods that cannot be manipulated. The key to avoiding this problem is to design experiments and place predictor variables in advance. Whenever possible, it is also helpful to collect extra statistics.

The statistical literature offers several methods for quantifying the degree of collinearity. One such method is the condition index, which uses the square root of the ratio of the largest and smallest eigenvalues of a variable set. Condition indexes are also used to assess the degree of multicollinearity. These are not the only types of collinearity.

Null hypothesis

The null hypothesis is the formal way to decide whether a statistical relationship in a sample was caused by chance or by an effect. Often symbolized by H0-naught, this hypothesis states that the result was unaffected by chance. In practice, the null hypothesis is used when there is no evidence to support a particular hypothesis. Therefore, a study’s results can be considered unreliable, but the null hypothesis is always correct.

The null hypothesis can be a good test for comparing the proportions of two groups. A vaccine experiment, for example, compares the infection rates in the treatment group to the control group. If a vaccine results in the same number of infections in each group, the null hypothesis states that the two groups are not significantly different. Conversely, an alternative hypothesis states that there are differences between the two groups. While it’s more difficult to test a null hypothesis, there are many ways to test the results of a study.

Probability of test being true by chance alone

In statistical analysis, P value is a measure of the likelihood that a test is true or false. For example, P = 0.05 means that there is a one percent chance that the test result is true, while P = 0.40 means that there is an eight percent chance that it was produced by chance alone. The lower the P value, the greater the likelihood that the test result is false. If the P value is higher than the expected value, the null hypothesis should be rejected.

P(B) is the unconditional probability of a test being true. It equals 198/10000, which means that there are 99 people in every thousand who will have a positive result. Therefore, the probability that you have the disease is 0.0198. However, if you are a woman, your P(B) is 0.278. If the test results show that you have HIV, then your P(B) is 0.00099.

Experimental designs

There are various types of experimental designs. Some are natural, such as comparing the educational experiences of first-born children with those of middle-born children. Others are artificial, such as studies that ask mothers if they smoked during pregnancy and then assign them to one of the groups. Randomization is impossible in these cases, so a quasi-experimental design is used. These designs are important because they allow researchers to compare the differences among groups that are unlikely to be caused by chance.

Randomization is another important principle of experimental designs. It means assigning treatment groups to experimental units randomly. This ensures that every allotment of subjects will have an equal probability. The experimental condition is then measured, and the treatment is the condition that causes the effect to occur. Randomization allows the experimenter to estimate the statistical error that might result from this treatment. The more replicates the treatment group receives, the smaller the standard error of mean (SEM).