BANCROFT'S INTRODUCTION TO BIOSTATISTICS

Introduction to Biostatistics

Introduction to biostatistics: Part 2, Descriptive statistics.

Descriptive statistics include measures of central tendency and variability. Measures of central tendency include mean, median, and mode. The mean is the arithmetic average of data from interval or ratio scales. The median reflects the 50th percentile score. The mode is the most frequently occurring value of a data distribution. Measures of variability include range, interquartile range, standa...

Tutorial in biostatistics. An introduction to hierarchical linear modelling.

Hierarchical linear models are useful for understanding relationships in hierarchical data structures, such as patients within hospitals or physicians within hospitals. In this tutorial we provide an introduction to the technique in general terms, and then specify model notation and assumptions in detail. We describe estimation techniques and hypothesis testing procedures for the three types of...

Introduction to biostatistics: Part 3. Statistical approaches to uncertainty: P values and confidence intervals unpacked.

(the difference in risk) is estimated to be 19.6% with a 95% CI of 5.7% to 33.6%. The P value of 0.006 means that an ARR of 19.6% or more would occur only in 6 in 1000 trials if streptomycin was equally as effective as bed rest. Since the P value is less than 0.05, the results are statistically significant (i.e., it is unlikely that streptomycin is ineffective in preventing death). The 95% CI s...

Introduction to biostatistics: Part 5, Statistical inference techniques for hypothesis testing with nonparametric data.

Specific statistical tests are used when the null hypothesis (H0) is to be tested using nonparametric nominal or ordinal data. With nominal data, experimental results are expressed by proportions or frequencies. Chi-square or related tests (the Fisher's exact test or the rows by columns test) are appropriate for testing H0 with nominal data. Ordinal data permit arrangement of statistical result...