


Sherril M. Stone, Ph.D. 

Department of Family Medicine 

OSUCollege of Osteopathic Medicine 




A set of methods and rules for organizing and
interpreting data 

Alone a statistic canÕt lie Ð it is what people
do with statistics that leads to problems 





Statistics are a common part of everyday life 

crime rates 

average time of possession in a sports game 

different polls 

They answer questions 

Does a particular surgery really work? 

Is Treatment A better than Treatment B? 

Do smokers get lung cancer more than
nonsmokers? 






POPULATION  the entire group a researcher
wishes to study 

SAMPLE  a subset of the population 

PARAMETER Ð 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 

a. Quantitative
(continuous) Ð amount, degree of the variable 

b. 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 





Nominal scale 

difference only, numbers have no quantitative
value 

Ex: 1 = female, 2 = male 

Ordinal scale 

rank order, numbers are greater than or less
than 

1 = best, 2 = better, 3 = good 

Interval scale 

equal intervals, distance between numbers is
equal 

Inch marks on a ruler 

Ratio scale 

true zero point, absence or presence of variable 

weight, height, temperature (Kelvin scale) 







Descriptive Statistics 

summary numbers computed on raw data 

Mean, Standard deviation, Variance, Correlation 

Inferential Statistics 

generalizations from sample to population 

ttest, ANOVA, Multivariate 






Variables and individual scores 

Capital letters, (X, Y) indicate variables 

The score for subject 4 would be written X_{4} 

Sums 

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 

Raw data
X_{1} X_{2} X_{3} X_{4} 

3 5 1 2 

Note: the sample size is n = 4 






General Rule  carry out all to four decimal
places then round 

Above .50
round up 

7.3369 rounds up to 7.34 

7.3351 rounds up to 7.34 

Below .50
round down 

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 E3 in exponential notation 

E3 signifies that the decimal place is really
three places to the left 

