Biostatistics Introduction & Data Presentation
Biostatistics
Introduction
What is Biotatistics?
What is Statistics?
Andy Chang
Youngstown State University
Lies and nothing but lies!?
Scientific method for understanding
and solving problem!
1
Why Statistic

Descriptive Statistics
Measure of Central Tendency
Numerical Summary
Measures
Mean: the average value of the data.
If n observations are denoted by x1, x2, ., xn,
their (sample) mean is
Describe Distribution with Numbers
Measure of Center
Measure of Var

Probability
A Simple Example
Probability and Counting Rules
A researcher claims that 10% of a large
population have disease H.
A random sample of 100 people is taken
from this population and examined.
If 20 people in this random sample have the
disease, w

Bayes Theorem & Screening Tests
Some Questions
Bayes Theorem
&
Diagnostic Tests
Screening Tests
If you test positive for HIV, what is
the probability that you have HIV?
If you have a positive mammogram,
what is the probability that you have
breast cance

Sampling Distribution & Confidence Interval
A Normal Distribution
P(X > 225) = .382
?
X ~ N ( = 211, = 46)
Example: Consider the distribution of serum
cholesterol levels for 40- to 70-year-old
males living in community A has a mean of
211 mg/100 ml, and t

One-Sided Confidence Interval
Size of Interval
Two-Sided C. I.
_
x
0.025
.95
-1.96x
s
s
, X + Z / 2
)
n
n
Z C.I.: ( X Z / 2
0.025
X
+1.96x
t C.I.: ( X t / 2
s
s
, X + t / 2
)
n
n
95% Samples
1
2
Lower Interval
One-Sided C. I.
Upper bound
_
x
Z C.I.:
s

Examples for Inference on MultipleSamples and
Nonparametric Tests
1. A researcher wishes to find out whether a new diet
program can help a particular population in reducing Body
Mass Index (BMI). The BMI scores from a random sample
of subjects were record

Normal Distribution
Relative Frequency Histogram
Percent
Modeling Continuous Distribution
Test scores
10 20 30 40 50 60 70 80 90 100 110
Normal Distribution
1
2
Density Curve
Continuous Distribution
Density Function (Curve)
Percent
A smooth curve that fit