12.1 – Experiments, Surveys, &
Observational Studies
• Survey – data are from responses given by a
sample and used to make a general conclusion
about the population.
• Survey – data are from responses given by a
sample and used to make a general conclusion
about the population.
• Population – the group being studied
• Survey – data are from responses given by a
sample and used to make a general conclusion
about the population.
• Population – the group being studied
• Census – a survey in which the entire
population is polled.
• Survey – data are from responses given by a
sample and used to make a general conclusion
about the population.
• Population – the group being studied
• Census – a survey in which the entire
population is polled.
• Sample – a smaller portion of the population
that is polled.
• Survey – data are from responses given by a
sample and used to make a general conclusion
about the population.
• Population – the group being studied
• Census – a survey in which the entire
population is polled.
• Sample – a smaller portion of the population
that is polled.
• Biased (survey) – a survey in which the design
favors a certain outcome.
• Survey – data are from responses given by a
sample and used to make a general conclusion
about the population.
• Population – the group being studied
• Census – a survey in which the entire population
is polled.
• Sample – a smaller portion of the population that
is polled.
• Biased (survey) – a survey in which the design
favors a certain outcome.
• Unbiased (survey) – a survey in which the design
is not based on any predetermined characteristics
of the population.
Ex. 1 State whether each survey would produce
a random sample. Write yes or no and explain.
Ex. 1 State whether each survey would produce
a random sample. Write yes or no and explain.
a) Asking every tenth person coming out of a
theater how many times a week they go to
the theater to determine how often city
residents support the performing arts.
Ex. 1 State whether each survey would produce
a random sample. Write yes or no and explain.
a) Asking every tenth person coming out of a
theater how many times a week they go to
the theater to determine how often city
residents support the performing arts.
No, b/c those people may go to the theater
more than the average person.
Ex. 1 State whether each survey would produce a
random sample. Write yes or no and explain.
a) Asking every tenth person coming out of a
theater how many times a week they go to the
theater to determine how often city residents
support the performing arts.
No, b/c those people may go to the theater
more than the average person.
b) Surveying people going into a pet store to find
out if the city’s residents support the building
and maintaining of a dog park.
Ex. 1 State whether each survey would produce a
random sample. Write yes or no and explain.
a) Asking every tenth person coming out of a
theater how many times a week they go to the
theater to determine how often city residents
support the performing arts.
No, b/c those people may go to the theater
more than the average person.
b) Surveying people going into a pet store to find
out if the city’s residents support the building
and maintaining of a dog park.
No, b/c those people may be more likely to
support a dog park than the average person.
Ex. 1 State whether each survey would produce a random sample.
Write yes or no and explain.
a)
Asking every tenth person coming out of a theater how many
times a week they go to the theater to determine how often city
residents support the performing arts.
No, b/c those people may go to the theater more than the
average person.
b)
Surveying people going into a pet store to find out if the city’s
residents support the building and maintaining of a dog park.
No, b/c those people may be more likely to support a dog park
than the average person.
c)
A box contains the name of every student in the school. A
hundred names are randomly pulled out of the box. Those
students are asked their opinions on the new cafeteria rules.
Ex. 1 State whether each survey would produce a random sample.
Write yes or no and explain.
a)
Asking every tenth person coming out of a theater how many
times a week they go to the theater to determine how often city
residents support the performing arts.
No, b/c those people may go to the theater more than the
average person.
b)
Surveying people going into a pet store to find out if the city’s
residents support the building and maintaining of a dog park.
No, b/c those people may be more likely to support a dog park
than the average person.
c)
A box contains the name of every student in the school. A
hundred names are randomly pulled out of the box. Those
students are asked their opinions on the new cafeteria rules.
Yes, b/c everyone as an equal chance of being selected.
Ex. 2 Chris wants to determine the most desired
location for the senior class trip. Which
questions will get him the answer he is seeking?
Ex. 2 Chris wants to determine the most desired
location for the senior class trip. Which
questions will get him the answer he is seeking?
a) Do you like Disneyland?
Ex. 2 Chris wants to determine the most desired
location for the senior class trip. Which
questions will get him the answer he is seeking?
a) Do you like Disneyland?
b) Which is better, King’s Island or Cedar Point?
Ex. 2 Chris wants to determine the most desired
location for the senior class trip. Which
questions will get him the answer he is seeking?
a) Do you like Disneyland?
b) Which is better, King’s Island or Cedar Point?
c) Where would you most like to go on the
senior trip?
Ex. 2 Chris wants to determine the most desired location
for the senior class trip. Which questions will get him the
answer he is seeking?
a) Do you like Disneyland?
b) Which is better, King’s Island or Cedar Point?
c) Where would you most like to go on the senior trip?
Option “c” would be the best question to ask. Option “a”
only asks about Disneyland and option “b” only asks
about King’s Island or Cedar Point. Both are limited and,
therefore, biased.
• Observational Study – data are recorded after
just observing the sample and used to
compare reactions and draw a conclusion
about responses of the population.
• Observational Study – data are recorded after
just observing the sample and used to
compare reactions and draw a conclusion
about responses of the population.
• Experiment – data are recorded after changing
the sample and used to make general
conclusions about what will happen during an
event.
• Observational Study – data are recorded after
just observing the sample and used to
compare reactions and draw a conclusion
about responses of the population.
• Experiment – data are recorded after changing
the sample and used to make general
conclusions about what will happen during an
event.
• Treatment Group – the people, animals, or
objects given the treatment.
• Observational Study – data are recorded after
just observing the sample and used to
compare reactions and draw a conclusion
about responses of the population.
• Experiment – data are recorded after changing
the sample and used to make general
conclusions about what will happen during an
event.
• Treatment Group – the people, animals, or
objects given the treatment.
• Control Group – the people, animals or
objects given a placebo, or false treatment.
Ex. 3 State whether each situation represents
an observational study or experiment. If it is an
experiment, identify the treatment & control
groups. Then determine if there is bias.
Ex. 3 State whether each situation represents
an observational study or experiment. If it is an
experiment, identify the treatment & control
groups. Then determine if there is bias.
a) Find 200 students, half of whom participated
in extracurricular activities, and compare
their grade-point averages.
Ex. 3 State whether each situation represents
an observational study or experiment. If it is an
experiment, identify the treatment & control
groups. Then determine if there is bias.
a) Find 200 students, half of whom participated
in extracurricular activities, and compare
their grade-point averages.
Observational Study
Ex. 3 State whether each situation represents an
observational study or experiment. If it is an
experiment, identify the treatment & control
groups. Then determine if there is bias.
a) Find 200 students, half of whom participated in
extracurricular activities, and compare their
grade-point averages.
Observational Study
b) Find 200 people and randomly split them into
two groups. One group jogs 2 miles per day and
the other group does not jog at all.
Ex. 3 State whether each situation represents an
observational study or experiment. If it is an experiment,
identify the treatment & control groups. Then determine
if there is bias.
a) Find 200 students, half of whom participated in
extracurricular activities, and compare their gradepoint averages.
Observational Study
b) Find 200 people and randomly split them into two
groups. One group jogs 2 miles per day and the other
group does not jog at all.
Experiment b/c put into groups and each group has
something done to it. The group that jogs is the
treatment group and the group that doesn’t jog is the
control group.
Ex. 4 Determine whether each situation calls for
a survey, an observational study, or and
experiment. Explain your reasoning.
Ex. 4 Determine whether each situation calls for
a survey, an observational study, or and
experiment. Explain your reasoning.
a) You want to test a treatment for a disease.
Ex. 4 Determine whether each situation calls for
a survey, an observational study, or and
experiment. Explain your reasoning.
a) You want to test a treatment for a disease.
Experiment b/c you would need a control
group and a group to receive the treatment.
Ex. 4 Determine whether each situation calls for
a survey, an observational study, or and
experiment. Explain your reasoning.
a) You want to test a treatment for a disease.
Experiment b/c you would need a control
group and a group to receive the treatment.
b) You want to find opinions on a presidential
election.
Ex. 4 Determine whether each situation calls for a
survey, an observational study, or and experiment.
Explain your reasoning.
a) You want to test a treatment for a disease.
Experiment b/c you would need a control
group and a group to receive the treatment.
b) You want to find opinions on a presidential
election.
Survey b/c you are determining a conclusion
of a population.
Ex. 4 Determine whether each situation calls for a survey,
an observational study, or and experiment. Explain your
reasoning.
a) You want to test a treatment for a disease.
Experiment b/c you would need a control group
and a group to receive the treatment.
b) You want to find opinions on a presidential election.
Survey b/c you are determining a conclusion of a
population.
c) You want to find out if 10 yrs. of smoking affects lung
capacity.
Ex. 4 Determine whether each situation calls for a survey, an
observational study, or and experiment. Explain your
reasoning.
a) You want to test a treatment for a disease.
Experiment b/c you would need a control group and a
group to receive the treatment.
b) You want to find opinions on a presidential election.
Survey b/c you are determining a conclusion of a
population.
c) You want to find out if 10 yrs. of smoking affects lung
capacity.
Observational study b/c you would observe the effects
on people’s lung capacity who have smoked for 10 yrs.