Statistical Methods for Psychology

Exercises 507

scale of self-sufficiency. The ratings were done in a baseline session and at the end of training.

The data follow:

Reinforcement No Reinforcement

Baseline Training Baseline Training

893 5

575 5

32810

572 5

295 3

67610

586 9

654 5

473 7

495 5

Run the appropriate analysis and state your conclusions.

14.4 An experimenter with only a modicum of statistical training took the data in Exercise 14.3
and ran an independent-groups t test instead, using the difference scores (training minus
baseline) as the raw data.
a. Run that analysis.
b. Square the value of t and compare it to the Fs you obtained in Exercise 14.3.
c. Explain why is not equal to Ffor Groups.

14.5 To understand just what happened in the experiment involving the training of severely
developmentally handicapped children (Exercise 14.3), our original experimenter evaluated
a third group at the same times as he did the first two groups, but otherwise provided no spe-
cial treatment. In other words, these children did not receive reinforcement, or even the
extra attention that the control group did. Their data follow:
Baseline: 3585566634
Training: 4566477322
a. Add these data to those in Exercise 14.3 and rerun the analysis.
b. Plot the results.
c. What can you conclude from the results you obtained in parts (a) and (b)?
d. Within the context of this three group experiment, run the contrast of the two conditions
that you have imported from Exercise 14.3.
e. Compute the effect size for the contrast in part (d).

14.6 For 2 years I carried on a running argument with my daughter concerning hand calculators.
She wanted one. I maintained that children who use calculators never learn to do arithmetic
correctly, whereas she maintained that they do. To settle the argument, we selected five of
her classmates who had calculators and five who did not, and made a totally unwarranted
assumption that the presence or absence of calculators was all that distinguished these chil-
dren. We then gave each child three 10-point tests (addition, subtraction, and multiplica-
tion), which they were required to do in a very short time in their heads. The scores are as
follows:
Addition Subtraction Multiplication
Calculator owners 85 3
75 2
97 3
63 1
85 1

t^2

(continues)