Sherril M. Stone, Ph.D.
Department of Family Medicine
OSU-College of Osteopathic Medicine
What are Statistics?
A set of methods and rules for organizing and interpreting data
Alone a statistic can’t lie – it is what people do with statistics that leads to problems
Why Do I Need Stats?
Statistics are a common part of everyday life
average time of possession in a sports game
They answer questions
Does a particular surgery really work?
Is Treatment A better than Treatment B?
Do smokers get lung cancer more than non-smokers?
POPULATION - the entire group a researcher wishes to study
SAMPLE - a subset of the population
PARAMETER – a characteristic of a population
VARIABLE - anything measured about the participants/subjects
Dependent - what is measured, it is the outcome variable
Independent - what the researcher manipulated or controlled
Quantitative (continuous) – amount, degree of the variable
Qualitative (categorical, nominal) - categories
RAW DATA - the actual numbers collected
Data is a plural noun
Correct: The data are presented in Table 1
SAMPLE STATISTIC - a summary measure of the sample
difference only, numbers have no quantitative value
Ex: 1 = female, 2 = male
rank order, numbers are greater than or less than
1 = best, 2 = better, 3 = good
equal intervals, distance between numbers is equal
Inch marks on a ruler
true zero point, absence or presence of variable
weight, height, temperature (Kelvin scale)
Types of Procedures
summary numbers computed on raw data
Mean, Standard deviation, Variance, Correlation
generalizations from sample to population
t-test, ANOVA, Multivariate
Variables and individual scores
Capital letters, (X, Y) indicate variables
The score for subject 4 would be written X
The upper case Greek sigma to indicate "the sum of"
Lower case n for the number of subjects in a sample
Upper case N for the number of subjects in population
3 5 1 2
Note: the sample size is n = 4
General Rule - carry out all to four decimal places then round
7.3369 rounds up to 7.34
7.3351 rounds up to 7.34
7.3328 rounds down to 7.33
7.3349 rounds down to 7.33
Exactly at .50
round to an even number.
7.3350 rounds to 7.34, up a bit
7.3450 rounds to 7.34, down a bit
7.3450001 rounds to 7.35, 50001 is slightly higher than .50.
Exponential notation on calculators
3/524 = .00572519084 =
5.72519084 E-3 in exponential notation
E-3 signifies that the decimal place is really three places to the left
Division of Research