2. Average cost of an airline meal
U.S. children who have high cholesterol
Average amount spent for a Father’s Day gift
3. Population
◦ The large, more general group from which the
sample group is gathered
Sample
◦ The specific group being studied
Population parameters
◦ The study (topic) that we wish to discover for the
entire group (population)
Sample statistics
◦ The study (topic) that actually characterizes the
small group (sample)
4. A research team determines the average
height and weight of U. S. college football
quarterbacks by gathering data from 10
colleges in the South.
Population = all U.S. college football quarterbacks
Sample = all quarterbacks from the 10 Southern colleges
Population parameters = average heights and weights of all
U.S. college football quarterbacks
Sample statistics = average heights and weights of the
quarterbacks from the 10 Southern colleges
5. There are four ways to choose a sample:
◦ Random sampling
◦ Systematic sampling
◦ Convenience sampling
◦ Stratified sampling
6. Choosing the people or things “any old way
we want to do it”
Example: Draw names out of a hat
Example: Get names from a list
Example: Nursing supervisors are selected to
determine yearly salaries
7. A “math” method is used to select the sample
(look for a 5th, 7th, or similar number)
Example: Number each subject in the
population and select every “nth” person
(every 4th person, every 10th person, etc.)
Example: Every 7th customer entering
Cleveland Mall is asked to select his or her
favorite store
Example: Every 100th hamburger made is
checked to determine its fat content
8. Like the convenience store idea, the sample is
selected because the people or things happen
to be at the right place at the right time
Example: ask people in a local mall
Example: ask people in a classroom
9. Divide population into groups according to
some characteristic – then make your sample
by “picking some from each group”
Example: Get opinions at CCC from first-year
students and second-year students
Example: Mail carriers are grouped by gender
and according to whether they walk or ride on
their routes. Ten selected from each group to
see if they have ever been bitten by a dog
10. Observational study
◦ Researchers simply “look at / watch / observe” the
sample without interfering or imposing conditions
on the sample
Experiment study
◦ Researchers apply a condition or a treatment to part
of the sample (or all of the sample) to see if that
condition / treatment has any affects on the study
11. Example: Data collected on ages and
incomes of motorcycle owners to see if
otorcycle owners are getting older and richer
Researcher stood at busy intersection to see
if color of car that a person drives is related
to running red lights
12. Divide Va Tech students into two groups to
do “sit up” exercises
One group told “do your best”
Other group told “ increase number of sit ups
by 10% more each day”
Subjects assigned to a group. Each group
placed on low fat, high fish, combo, or
regular diet. Blood pressures compared after
6 months to see if diet has effect on BP.
13. Qualitative Data
◦ Deals with descriptions
◦ Can be observed and is “non-numerical”
Quantitative Data
◦ Deals with numbers
◦ Can be measured and/or counted
14. Marital status of hospital nurses
Colors of cars in CCC parking lot
A person rating a movie (four stars, three stars, etc.)
15. Time it takes to run a kilometer
Weight of lobsters in a tank at a restaurant
Ounces of fruit in a smoothie
Seating capacity of football stadium
Age of people living in nursing home
