Following
procedures suggested by Nunnally (1978) and outlined by Gable
(1986), a number of studies were conducted that would examine
the factorial validity of the Teacher Stress Inventory. The
first, conducted on the Connecticut data collected using the
Teacher Stress Scale pilot form, resulted in a sixfactor
solution (Fimian, 1985). Then, with the additional items added
to the pilot form, the second set of factor analyses was
conducted using this pilot form to collect data from the Vermont
teachers; this, too, resulted in the sixfactor version of the
TSI form (Fimian, 1984b).
Samples
These teachers,
representing 21 individual samples from eight states, provided
data for the most recent round of TSI development activities.
Sample designations, descriptions, and related information are
presented in
Table 10
. Of these, 13 samples' inventories were
distributed through the mail; the balance of the data were
collected either at workshops or through regional surveys. More
detailed information regarding these samples can be found in
Fimian (1983), Courtney (1987), Honaker (1987), and Zacherman
(1984). Of these 3,401 teachers, 743 were included in all
regular teachers" samples, 1,778 were included in "all
special education teacher" samples, and 880 were grouped in
combined special/regular teacher samples; of this last group, 88
were unclassifiable, and the majority were special education
teachers. Thus, the final counts were 960 (regular education),
2,353 (special education), and 88 (unclassified by group), for a
total of 3,401 teachers.
The majority of the
teachers in the norm sample were female (n = 2,56 1; 75%), and
the balance were male (n = 726; 21 %; some percentages may not
sum to 100% due to missing cases and/or rounding error). Many
were in their twenties (n = 1,292; 38%), with the remainder in
their thirties (n = 1,398; 41%), their forties (n = 386; 11%),
or fifty or older (n = 164; 8%). They included secondary school
teachers (n = 1,420; 42%), elementary school teachers (n = 791;
23%), or middle school teachers (n = 499; 15%). The majority had
less than 10 years' experience (n = 2,092; 62%), whereas the
balance reported more. The minority reported teaching fewer than
20 students per day (n = 1,008; 37%), and the rest reported more
than 20 (n = 1,728; 51%). A minority had achieved a bachelor's
degree (n = 450; 13%), the balance an advanced degree.
Statistical Analyses
Based on the teacher
data, and in order to identify stress factors, preliminary
principal components factor analyses were conducted and followed
by oblique and varimax rotations using the stress strength data
collected in questions 1 through 49, according to an instrument
development model proposed elsewhere (Child, 1970; Nie, Hull,
Jenkins, Steinbrenner, & Bent, 1975) and later expanded upon
by Gable (1986). Then, the internal consistency reliability
estimates for the TSI subscales and scale were examined using
Cronbach's coefficient alpha (Hull & Nie, 1981; Nunnally,
1978). Once valid and reliable TSI subscales and scores were
identified, the relationships among these were investigated
using Pearson productmoment correlational analyses. The
factorial validity of the revised TSI was examined using the 49
TSI items. Preliminary principal components analyses were
conducted and followed by oblique and varimax rotations. Based
on the 49by49 item intercorrelation matrix and the principal
components analyses, 10 factors for the stress strength
dimension emerged that accounted for 58% of the stress variance;
only factors with eigen values exceeding 1.0 were retained. An
initial inspection of the factor patterns indicated 10 discrete
factors.
Then, one set of
selection criteria was applied to each of the 49 items. Items
were retained that (a) had factor loadings of .35 or greater on
the stress strength dimension, (b) loaded clearly on only one
factor (i.e., simple structure was achieved), and (c)
contributed to the subjective interpretability of the particular
factor on which the item loaded. Once the factors were
identified, the TSI's internal consistency or alpha reliability
estimates were then examined. One estimate was generated for
each of the 10 stress strength subscales. Also, one estimate was
generated for the total group of items. Then, any item that did
not reduce the internal consistency reliability of the
particular subscale in which it was nested was retained. Factors
whose alpha reliability estimates exceeded .60 were retained;
exploratory alpha ranges of .60 to .90 for the TSI subscales and
.85 to .95 for the TS1 scale were targeted. Final acceptance or
deletion of the TSI items, therefore, was based on a combination
of findings from each of the analyses. Items were kept that were
not only valid in terms of subscale/scale factorial validity,
but also reliable in terms of subscale/scale internal
consistency reliability.
Results
Table 11
contains the
49 retained and abbreviated item stems with their communalities
and component loadings derived from the oblique rotations for
the stress strength measures for each of 10 resulting factors.
Employing a root criterion of unity, the 10component solution
derived from the strength item scores accounted for 58% of the
total stress strength variance associated with the item
interrelationships. It was evident from Table 11 that (a) 10
discrete and interpretable factors resulted and (b) of the
original 49 items, all exceeded the .35 loading criterion with
all but 2 exceeding .40. Thus, no items were deleted from the
pool. All items included in the initial form of the TSI were
retained for the final form.
The percentage of
explained variance per factor was then calculated by summing
each of the squares of their correlation coefficients listed on
the varimax factor correlation matrix and then dividing this sum
by the number of entries (i.e., 49); perfactor contributions
were then summed. Lotus 123 (Version 2.0) was used to conduct
all calculations.
Since only the stress
strength dimension was under investigation, one total score for
that dimension was developed using the item mean data. Also,
since the stress strength dimension is collectively defined in
terms of the 10 factors, item mean scores were used to develop
10 conceptually similar subscales. Subscale scores were derived
by first summing the item scores for the stems nested within
each subscale and then dividing the resulting value by the
number of items in that particular subscale. In this fashion,
each subscale's score falls within the 1to5point strength
range. Thus, the relative strength of each collective body of
stressful events (hereafter termed "subscale') can be
easily interpreted. Insofar as the overall stress experienced by
teachers is operationally defined as the relative strength with
which all 49 events are experienced, the 10 stress strength
subscale scores were first summed and then divided by the total
number of stress factors for a Total Stress Strength Score. By
so doing, the resulting Total Stress Strength Score should fall
within the 1to5point strength range, and the relative
strength of stressful events can be easily interpreted.
