In this lecture we will review basic statistical concepts.   This lecture is written by Dr. Maria Correa-Prisant, Dept. of Microbiology, Pathology, Parasitology, College of Veterinary Medicine , North Carolina State University    Original PowerPoint file of this lecture

Compared to clinical work, this is the way we get to know our client the "data set."

There are many different types of variables and it is important that we recognize them since different statistical analyses are needed.

These are pictoral representations of different distributions for continuous data.

You CANNOT use tests developed for continuous data with ordinal or nominal variables.

The mean, median, and mode coincide when you have normally distributed data.

Only for continuous data.

When the data are not normally distributed, the mean may not be the appropriate measure of central tendency.

http://en.wikipedia.org/wiki/Descriptive_statistics Descriptive statistics From Wikipedia, the free encyclopedia

Dispersion of the data can be expressed using the standard deviation (SD) or percentiles. Use of SD when data are not normally distributed may be innappropriate.

2 standard deviation (SD) are commonly used 2 standard deviation (SD) are commonly used. Mean and Standard Deviation

Simply divide the data into 100 pieces Simply divide the data into 100 pieces. Percentiles are not dependent on the distribution of the data.

Data Display and Summary

Data Display and Summary

The mean of the means is obtained first The mean of the means is obtained first. Then calculated the standard error (SE) of that mean of means. Populations and samples

For categorical data you CANNOT calculate the mean For categorical data you CANNOT calculate the mean. It does not make sense!

Drawing or setting up your data into R by C tables may help you to get a better feeling for the case.

With statistical tests we determine association. We do not "prove" With statistical tests we determine association. We do not "prove". We say: we either do not have enough evidence or we do to reject the Ho.

Review Questions (Developed by the Supercourse team) Describe different types of variables Describe different types of data distribution What is association and what is the relationship between association and causation? We would appreciate your help with evaluating the content of this course. Please send completed Evaluation Form  to super1@pitt.edu  with the subject "chronic disease supercourse evaluation"   If you have any comments or questions, please send a message to super1@pitt.edu