Psychology 100A – HW1 solution
(2) (adapted from Kiess)
Students learning the basic ballet positions often have
difficulty assuming the correct foot position. One problem is foot pronation, (the foot
rolling in when the heals are placed together and the toes point laterally outward). To
help students overcome this problem, Clarkson et al. (1986) formed two equivalent
groups of women who had no previous ballet training. Both groups were taught the basic
ballet positions and the amount of time the feet pronated was measured. For one group, a
student was warned by a buzzer when her foot pronated. Students in the other group
received no feedback. Clarkson et al. found that the subjects with buzzer feedback had
only 3.1 seconds of foot pronation while the subjects without feedback had 21.8 seconds
of feet pronation. A statistical tests confirmed that the difference in foot pronation was
not due to chance.
(A) What population do these subjects belong to?
Women with no previous training in ballet interested in taking a ballet class.
(B) Suggest a way of making the two groups equivalent.
As each woman enters the class, flip a fair coin to randomly decide to which group
(intervention or control) she is assigned.
(C) What is the independent variable manipulated by Clarkson et al.?
(1) feedback
(2) basic ballet positions
(3) degree of pronation
(4) time
(5) none of the above
(1) The grouping variable feedback – buzzer feedback vs. no buzzer feedback
(D) The independent variable is
(1) a ratio measurement
(2) a nominal measurement
(3) an ordinal measurement
(4) an interval measurement
(5) none of the above, we classify only dependent variables
(2) The variable is nominal.
(E) Is it discrete or continuous?
It can be coded as a 0 or 1 and therefore can be considered discrete.
(F) What is the dependent variable measured by Clarkson et al.?
(1) feedback
(2) basic ballet positions
(3) degree of pronation
(4) time
(5) none of the above
(4) The amount of time feet are pronated.
(G) Is the dependent variable is a
(1) a ratio measurement
(2) a nominal measurement
(3) an ordinal measurement
(4) an interval measurement
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View Full Document(5) none of the above, we classify only independent variables
(1) The variable is a ratio measurement (zero value has meaning).
(H) Is it discrete or continuous?
It is continuous.
(I) This study uses
(1) naturalistic observations
(2) archival records
(3) survey research
(4) simulated observations
(5) experimental observations
(5) The study is an experiment because it is carefully controlled study in which the
independent variable is manipulated to determine the effect on dependent variable.
(J) Explain why statistical hypothesis testing is necessary in this case?
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 Winter '10
 NANDY
 Psychology, Level of measurement, Kiess, basic ballet positions

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