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A 100-item test was split into two halves, and the
split-half coeffi cient of correlation was found to be .60. Calculate the
reliability coeffi cient for the full-length test.

1. You have the following technical information from two
tests: On which test would a student’s score be expected to fl uctuate the most
on repeated administrations?
2. What are the sources of error that affect the reliability
of a test? Give an example of each.

Evaluate the following research designs with respect to
methods used and the control provided. Make suggestions for improvements if
needed.
a. A researcher wanted to ascertain if homogeneous grouping
improves learning in a fi rst course in biology. The researcher designated one
of two high schools in a small city to serve as the experimental school and the
other as the control. Both schools had approximately the same number of
students in each of four sections of science. In the experimental school,
pupils were grouped homogeneously on the basis of aptitude and scores on
achievement tests in science. In the control school, pupils were placed in
sections at random. At the end of the year, all pupils were given a
standardized test in biology. Statistical tests showed the experimental group
to be superior on the test. The researcher concluded that homogeneous grouping
results in greater learning in biology.
b. A history teacher was concerned about her students’ lack
of knowledge of their state and national governments and of current events. She
decided to experiment with some new materials and methods to determine if she
could obtain improvement. In classes A and B, she introduced the new materials
and methods. In classes C and D, she used the traditional methods. Classes A
and B were administered both the pretest and the posttest; classes C and D were
administered only the posttest. When comparisons were made on the posttest, classes
A and B were found to be superior. Their superior performance was attributed to
the new materials and methods.

Identify the threats to internal validity in each of the
following experimental studies:
a. At the beginning of the school year, an elementary
teacher set up reading stations in her room with supplementary reading
materials in each. At the end of the year, she reported that the interest of
her class in reading was higher than in any of her previous classes. She
recommended that all teachers set up reading stations.
b. A researcher wanted to investigate the effectiveness of
new teaching materials designed to increase students’ verbal skills. One class
used the new materials, and another class used conventional workbooks. Both
classes were given a test of verbal skills at the end of the semester.
c. A study was conducted in three thirdgrade classrooms
investigating the effect of three methods of teaching math. The teacher could
choose the method she wanted to use but could use only one method with her
students. At the end of the semester, all the third-graders were given the same
math achievement test.

Identify the threat to external validity in the following
examples:
a. A teacher read research reporting great results from
using a particular remedial reading program. She tried the program in her
classroom but did not get the same results.
b. A teacher read about a new method of instruction that was
very successful with regular classes. The method did not work when she tried it
with her special education students.
c. A research journal reported that a new antismoking fi lm
had brought about a signifi cant change in students’ attitudes. After viewing
the fi lm, students expressed many more negative attitudes toward smoking than
they had on a prefi lm measure. A teacher decided to use the fi lm with his
middle school students but did not want to take time to administer the
“pretest.” He administered an attitude scale following the fi lm but did not fi
nd marked negative attitudes toward smoking.

What are the threats to internal validity in the following
examples?
a. Very obese individuals who go to a weight control clinic
will likely show some loss of weight even if the weight control treatment has
no effect.
b. A longitudinal study of the effectiveness of a study
skills treatment followed a group of college students. The results showed that
the seniors had a fi nal mean grade point average higher than they had as
freshmen

From a group of students enrolled in social
studies in a high school, a researcher randomly selected 60
students. The students
were then divided into two groups by
random assignment of 30 to group A, the
traditional social studies curriculum, and
30 to group B, a new program designed
to deal with the history of certain ethnic
groups. The two groups were compared at
the end of the semester on a scale designed
to measure attitudes toward ethnic groups.
In this study, identify the following:
a. Independent variable
b. Dependent variable
c. Control group
d. Experimental group
e. Method(s) used to control for differences
between the groups
f. Research design used
g. Any threats to internal validity

Consider the following research question: Does teaching the
fi rst year of French through an oral–aural approach, rather than the
grammar-transformational method, alter pupil performance on a standardized
year-end test in grammar, reading, and vocabulary?
a. Identify the ideal experiment to answer this question,
assuming that there are no administrative or other restrictions.
b. Identify the experiment that would most likely be required
in the typical high school setting.
c. State the relative advantages of the ideal experimental
design compared with the design.

Design the ideal experiment to test the following
hypothesis: Children who view fi lms of harmonious racial interaction will show
a more positive attitude toward racial minorities than will children shown fi
lms that depict racial confl ict