STAT 250.3: Introduction to Biostatistics Instructor: Efi Antoniou. Introduction. Highlights from the Syllabus. The course website will contain important information…so plan to access it frequently: http://www.stat.psu.edu/~antoniou/stat250.3
NOTE: Homework Problems/Solutions, and Study Guides will be Provided on the course web site.
When we have a question that needs answering, we use statistics as a method to find the answer. Statistics helps us to ask the right question, collect the right data, and make the correct conclusion.
Statistics is not just about number crunching! Critical thinking skills and common sense are far more important than mathematical ability.
2. Describe the SAMPLE
1. Draw a Representative SAMPLE from the POPULATION
3. Use Rules of Probability and Statistics to make Conclusions about the POPULATION from the SAMPLE.
T = (x – μ)/σ
P(x) = x(1-p)*(n-x)p
Smoking, weight and parent’s disease status are associated with heard disease in people 18 years of age and older.
e.g. Persons 18 years of age and older with heart disease.
e.g. 50 people 18+ years old with heart disease.
e.g. n = 50.
e.g. 50 sets of values for “smoking”, “weight” and “parents’ disease status – one for each individual.
1. How much do PSU students spend on books a semester?
2. What percentage of fire crackers produced by ACME Fire Cracker Company are defective?
1. 300 full time PSU students answered this question at the bookstore.
2. 200 firecrackers taken from one batch on June 15th, 2002.
It is often difficult to draw conclusions from raw data. It is helpful to summarize raw data in the form of tables or graphs for easier interpretation.
Consider data from the survey given to stat 200 students that asked their sex, preference for coke or pepsi, and the fastest speed they had ever driven. The raw data would look something like this:
Based on this data sheet it would be difficult to compare males and females in their choice of cola and fastest speed ever driven.
We use descriptive statistics to summarize raw data into tables, graphs, and numerical summaries.
Consider the previous data when we have summarized the variables using descriptive statistics. It is now easier to see differences between the sexes.
Variables Cola by Sex:Variables Fastest Speed by Sex:
Consider the following example:
Sarah conducts an experiment to determine whether a new type of high fat diet is better than the standard low fat diet. In her sample of 100 subjects (50 new, 50 old diet) she finds that those on the new diet lose an average of 10 lbs and those on the old diet lose an average of 8 lbs. Clearly in the sample the new diet was more effective than the old diet, but can we make this conclusion about the population? Is there enough evidence in the sample to suggest that the new diet is better for everyone, or could Sarah’s results have just been by chance (a lucky result)?
In this course we will learn statistical methods to answer Sarah’s question, and rules that help us draw conclusions about populations (what we are really interested in!) based on data from the sample.
Examples: height, number of siblings, IQ score.
Examples: eye color, country of residence, t-shirt size.