AP Statistics– Chapter 13 (Experiments)
Name: ______________________
Fill in the blank. No notes; no book! Treat this like a quiz.
1) _______________ in experimental design is akin to stratification in sample survey design.
2) When an observed difference is too large for us to believe that it is likely to have occurred
naturally, we consider the difference to be _______________ _____________.
3) An ____________ __________ is a study in which no manipulation of factors has been employed.
4) To be valid, an experiment must assign experimental units to treatment groups at ____________.
5) An ________________ manipulates factor levels to create treatments, randomly assigns subjects
to these treatment levels, and then compares the responses of the subject groups across treatment
levels.
6) An ___________ ________ is a variable whose levels are controlled by the experimenter.
7) A ____________ ________ is a variable whose values are compared across different treatments.
8) Individuals on whom an experiment is performed are called ________________.
9) The specific values that the experimenter chooses for a factor are called the ________________ of
the factor.
10) A _________________ is the process, intervention, or other controlled circumstance applied to
randomly assigned experimental units. They are different levels of a single factor or are made up
of combinations of levels of two or more factors.
11) A __________ __________ is the name for the experimental units assigned to a baseline
treatment level, typically either the default treatment, which is well understood, or a null, placebo
treatment. Their responses provide a basis for comparison.
12) Any individual associated with an experiment who is not aware of how the subjects have been
allocated to treatment groups is said to be ____________________.
13) A _____________ is a null treatment known to have no effect, administered for comparison
because many subjects respond to such a null treatment.
14) The _____________ ____________ is the tendency of many human subjects to show a response
even when administered a null treatment.
15) When the levels of one factor are associated with levels of another factor, we say that these two
factors are ________________.
16) A __________________ ___________ is an observational study in which subjects are selected
and then their previous conditions or behaviors are determined.
17) A ________________ _________________ is an observational study in which subjects are
followed to observe future outcomes.
18) The four principles of experimental design are: C___________, R______________,
R____________, and B_________.
19) There are two main classes of individuals who can affect the outcome of an experiment:
a. Those who could _____________ the results (the subjects, treatment administrators, or
technicians)
b. Those who ______________ the results (judges, treating physicians, etc.)
20) When both of these groups are unaware of who received which treatment, the experiment is said to
be _______________ __________.
21) In a _______________ _____________ design, all experimental units have an equal chance of
receiving any treatment.
22) In a ______________ ___________ design, the randomization occurs only within blocks.
23) In a retrospective or prospective study, subjects who are similar in ways not under study may be
_______ and then compared with each other on the variables of interest.
An article in a local newspaper reported that dogs kept as pets tend to be overweight.
Veterinarians say that diet and exercise will help these chubby dogs get in shape. The
veterinarians propose two different diets (Diet A and Diet B) and two different exercise programs
(Plan 1 and Plan 2). Diet A: owners control the portions of dog food and dog treats; Diet B: a
mixture of fresh vegetables with the dog food and substitute regular dog treats with baby
carrots. Plan 1: three 30-minute walks a week; Plan 2: 20-minute walks daily. Sixty dog owners
volunteer to take part in an experiment to help their chubby dogs lose weight.
1. Identify the following:
a. the subjects:
b. the factor(s) and the number of level(s) for each:
c. the number of treatments:
d. whether or not the experiment is blind (or double-blind):
e. the response variable:
2. Design an experiment to determine whether the diet and exercise programs are effective in
helping dogs to lose weight.
3. Say you wanted to block by breed. Draw the beginnings of an experimental design diagram.