EXPERIMENTAL RESEARCHusage, and ends with map reading. The teacher
gives tests to each class after each unit, and students
take a comprehensive exam at the end of the term.
The students were randomly assigned to classes, so
the instructor could see whether presenting units in
one sequence or another resulted in improved
learning.
Solomon Four-Group Design. We believe that the
pretest measure may have an influence on the treat-
ment or dependent variable. A pretest can some-
times sensitize participants to the treatment or
improve their performance on the posttest (see theInterrupted Time Series, Alcohol Sales, and Suicide
Rates) illustrated equivalent time series.
Latin Square Design. At times, we are interested
in how several independent variables in differ-
ent sequences or time orders affect a dependent
variable. The Latin square designenables us to
examine this type of situation. For example, a
geography instructor has three units to teach
students: map reading, using a compass, and the
longitude/latitude (LL) system. The units can be
taught in any order, but the teacher wants to know
which order most helps students learn. In one class,
students first learn to read maps, then how to use a
compass, and then the LL system. In another class,
using a compass comes first, then map reading,
and then using the LL system. In a third class, the
instructor first teaches the LL system, then compass
EXAMPLE BOX 3
Interrupted Time Series, Alcohol Sales, and Suicide Ratesdrunk-driving fatalities in the country. Many past
studies also showed a strong relationship between
suicide rates and alcohol consumption.
Zalcman and Mann (2007) used a three-stage in-
terrupted time-series design to examine the influ-
ence of Alberta’s privatization of alcohol sales on
suicide rates between 1976 and 1999. They consid-
ered whether suicide rates changed after each priva-
tization phase. They also compared Alberta’s suicide
levels to those for the same years in Ontario where
alcohol sales remained a government monopoly.
The researchers found that the 1985 privatization
of wine retailers increased male and female suicide
rates in Alberta by 51 percent for males and 35 per-
cent for females. After the 1989–1990 privatization
of spirits and wine a significant increase occurred in
male and female suicide rates, estimated to be 17 per-
cent and 52 percent, respectively. The 1994 privati-
zation event significantly increased male suicide
mortality rates, estimated at 19 percent, but not
female suicide rates. Part of the increase was a short-
term spurt but long-term suicide raises also rose.
By tracing the rates both over time by comparing
those in a “control group” or to those in Ontario,
the authors provided evidence of the effect of alco-
hol privatization.Governments face strong pressures by economic
interests to modify laws to allow them to collect
increased profits from alcohol sales. In most of west-
ern Canada, a public monopoly controlled alcohol
sales and distribution through most of the twentieth
century. Proponents of privatization point to its
economic benefits, including selling previously
government-owned retail outlets and the sale of
licenses to merchandise alcohol. Others point to the
impact of privatization on consumption and health.
Studies of privatization of sales of alcoholic bever-
ages indicate that privatization greatly expands
alcohol availability and consumption.
Alberta moved to privatize alcohol sales in three
stages: the opening of privately owned wine stores in
1985, the opening of privately owned cold beer
stores and sale of spirits and wine in hotels in the rural
area in 1989–1990, and finally the privatization of all
liquor stores in 1994. The number of alcohol outlets
increased substantially, and consumption of spirits
increased dramatically at a time when consumption
was decreasing elsewhere in the country. Privatiza-
tion in Alberta has been associated with an increase
in criminal offenses, such as liquor store break-ins
and less strict enforcement of underage purchase
laws. Alberta also has some of the highest rates ofLatin square design An experimental plan to exam-
ine whether the order or sequence in which participants
receive versions of the treatment has an effect.