|
Items in cart [0] |
Questions? Call 888-624-8373 |
| Copyright © 2009. National Academy of Sciences. All rights reserved. Terms of Use and Privacy Statement |
Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 91
APPENDIX B
SAMPLING METHODOLOGY
This section includes a detailed account of the various deci-
sions involved and the actual steps taken in selecting the sample and
in assigning respondents to interviewers. A representative sample
of the Port Jervis population was required in order to get an accurate
picture of how city residents reacted to the flood and threat of disas-
ter, as well as to test the various hypotheses which are included in
the main report.
A. Possible Sources for Sample Selection
In the course of the preliminary survey, a number of possible
sources of sampling information were discovered. These were (~) a
complete listing of all Port Jervis residences using the municipal
water supply, (2) the list of all registered voters in the last municipal
ele ction, ~ 3) a map of the city which contained contemporary informa-
tion on zoning regulations and dwelling-units, and (4) a recent issue
of the city directory.
Despite our interest in the non-residents (tourists) to the
false report, city officials, and various respondents, assured us that
all tourists had departed during the early phases of Me emergency.
Because of this, no attempt was made to include non-residents in our
sample .
The municipal water records were seriously contemplated as
a reasonably accurate and up-to-date source of resident sample data.
The chief reason for their abandonment was that each residence was
listed under the owner's name. In instances in which a number of in-
dividuals were living in a residence, the interviewer would have had
difficulty getting the correct respondent. This would not have been a
severe handicap except that the arrangement of the records did not
permit a simple discrimination between single and multiple dwelling-
units. The people in the Water Department suggested some rules-of-
thumb for deciding whether or not the residence was a multiple dwell-
ing -unit, but the e stimation p roc e s s would have tripled or quadrupled
the time involved in selecting respondents.
91
OCR for page 92
The second source we considered, the roster of registered
voters, was discarded because of its typical lack of representative-
ness.
The third source, the city ~nap, was found to be completely
inadequate for our purposes. Although the zones and zoning regula-
tions seemed to be indicated clearly, there was no means of deter-
mining the number of dwelling-units in any given area of the city.
The map s we re the refor e used only as a means of indicating the lo ca-
ti on of a r e spondent' s dwelling -unit onc e he had be en s ele cte d for the
sample.
The fourth source, the city directory, was finally selected
for sampling information. According to officials in the City Clerk's
Office and in the municipal water company office, the publisher of
the directory had canvassed the city during the early part of 1955.
The dir e cto ry was publi she d about Mar ch of 1 9 5 5.
Information from the aforementioned offices indicated that
minimum of individuals moved in and out of the city. This, coupled
with the fact that 1 95 0 census data indicated an unusually large propor -
tion of older people in the city, gave the investigators some assurance
that they were working in a community with a relatively stable popula-
tion. However, the use of this directory involved a calculated risk,
since it was at least eight months out of date. Despite this, it seemed
the most accurate source of information available and the sample was
selected from the listings it contained.
B. Selection of the City-Wide Sample
The city directory had the usual lists: an alphabetical list of
adults, and a street-by-street list of residences by address. Both of
these lists were used in the selection of the sample.
There were only approximately 5, 300 listings in the alpha-
betical list because wives whose husbands were living were noted
parenthetically after the listing for the husband, and because children
were not listed at all. It was decided that a minimum of a 1 per cent
sample of the total population of about 9, 700 residents was needed.
Accordingly, 110 random numbers under 5, 300 were selected from a
table of random numbers.
92
OCR for page 93
The numbers were arrange] in order of magnitude and mem-
bers of the sample were selected from the alphabetical list by count-
ing through until a given random number was reached. For example,
suppose that the first random number is twenty-five. The investigator
counted through the alphabetical list from its beginning, omitting all
business establishments and names of individuals living outside the
city limits, until he reached the twenty-fifth resident's name. This
name and address was then copied down as the first member of the
s ample . If the s e cond r ando ~ ~ ~ numb er was twenty - eight, the inve sti -
gator would count down three more names, and copy this name for
the second member of the sample. The procedure was continued until
all 110 members of the city-wi(Le sample had been selected.
As a proportional representation by sex was desired, the
s ex of the r e spondent in a given dwelling -unit was also determined
when the name was drawn. If the nth listing included the name of only
one man or woman, that name was included in the sample. If, on the
other hand, both a man and his wife were listed, the wife was selected
if the random number was even, the husband if the number was odd.
We anticipated that a number of residents would be unavail-
able for the period of the study. Therefore an additional group of
fifty random numbers was chosen so that replacements for the sample
. . ~ . ~ . ~ ~ ~
could be selected at random. These numbers were kept in the order
in which they were drawn from the table of random numbers. Thus,
an individual assigned a very high random number might be the first
one selected as a replacement for the sample.
C . Selection of the Saturation Sample
Only a small proportion of the city-wide sample lived in the
flooded areas. Because some of the hypotheses in the research pro-
posal involved a comparison between individuals who had evacuated as
a function of Friday's flood and those who had not, it was necessary
to increase the number of respondents in the flooded] portions of the
city. Accordingly, an additional sample was drawn in those areas of
the city which had been flooded.
_
This was done by s electing forty new random number s, which
were then arranged in order from the lowest to the highest. It was
not possible to use the alphabetical list which was used for the city
93
-
OCR for page 94
wide sample, because this list included individuals living anywhere in
the city. Instead, we first determined which residences were actually
in the flooded areas. Those residences which were on streets which
hac] been flooded were marked in the street section of the directory.
The investigator then counted from the beginning of each street to its
end (or to the end of the flooded area) until he came to the random
number assigned to a particular respondent. This process was con-
tinued until forty residents had been selected. An additional twenty
numbers were selected from the table and were arranged in the order
in which they were selected. These were kept on reserve for what-
ever replacements might be needed. As in the city-wide sample, the
interviewer asked for the woman of the house if the random number
was even, the man of the house if the number was odd.
D. Assignment of Respondents to Interviewers
When the interviewer was ready for an assignment, he re-
ported to the individual in charge of sampling, who gave him a street-
map of Port Je rvi s containing hi s as signment for that day. The name
and sex of each respondent and the approximate location of his dwell-
ing-unit were indicated on the map. An assignment usually included
about a half-dozen respondents, all located in a restricted geograph-
ical area to minimize travel cost and time between interviews. How-
ever, the use of this method raised the possibility of-introducing
some bias. If interviewers worked only in a particular area, differ-
ence s betwe en are as could po s sibly be attributable to inte rviewe r
differences, rather than to the respondents' socio-economic status,
experiences with the flood, interpretation of the false report, etc. In
order to circumvent this problem partially, interviewers were rotated
from one portion of the city to another whenever possible.
Having received his assignment, the interviewer attempted to
locate and interview each of his respondents. Upon his return to the
office, he reported on which interviews had been completed, which re-
spondents were unavailable but would be contacted later, and which
were completely inaccessible for the period set for the study. Where
respondents were inaccessible, replacements were assigned to the
interviewer. A check on all call-backs was made periodically to in-
sure that the interviewers were doing their best to obtain the respondent
indicated.
94
OCR for page 95
Additional checks on the performance of interviewers were
made to make sure that no one was falsifying data. Periodically, two
supervisors would contact several of the respondents who were re-
ported to have been interviewed. If this contact was made by telephone,
the supervisor would introduce himself and ask for an appointment
for an interview. If contact was made in person (at the respondent's
home) the interview was begun. When the supervisor was informed
that an individual from the Institute hac] already completed the inter-
view, contact was quickly terminated with an apology, and an explana-
tion to the effe ct that two indivi dual s we re customarily as signed the
same list and that the other person had obviously already reached the
respondent. art no case clid the supervisors final that an interviewer
hac] falsely reported a completed interview.
E. Replacements
All interviewers were instructed to make at least three call-
backs before asking for a replacement. In some cases as many as
six call-backs were made before a replacement was used. Specific-
ally, the interviewer s were given the following instructions:
111.
Your respondents will be assigned to you by name,
address and sex.
Go to that address and try to find the person designated.
(Make sure that the complete name is correct as there
may be a number of people in the house with the same
last name. ~
If the respondent is not at home, try to make an appoint-
ment for later on. If no one is at home, call back at a
later time. In any event, make at least three call-backs,
spaced far enough apart so that the respondent has a
chance to return. If unsuccessful then, call Dr. Thayer.
If the respondent has moved out of town, take the person
(preferably of the same sex) who is now living in his old
quarters. If the respondent has moved, but to some
other determinable place in town, go to that address and
interview him. (If this is at some distance from your
area, get your other interviews in the area first.
95
OCR for page 96
4. If the respondent is clearly inaccessible for the dura-
tion of the study, take the respondent in that dwelling-
unit who is of Me same sex as the clesignatecl person.
If the re is no one the re of that sex, s e e Dr . Thayer about
a replacement. "
In summary, the interviewers were told to take replacements
only if the re spondent de signaled was clearly inacce s sible. Under
this condition, he was to take a replacement of the original respondent's
sex, who lived in the designated dwelling-unit. If no such person
lived there, he was to get a replacement from the list of random num-
bers referred to above.
The proportion of r eplacements needed for the city sample
ran higher (21 per cent) than for the saturation sample (S per cent).
Althoughitis impossible to accountfor this difference with the data
available, a few hypotheses may be considered: (1) The people in the
saturation sample were more likely to be involved in repairing dam-
age to their home s and therefore were tempo rarity le s s mobile . (2)
The people in this area were less well-off financially both as a nor-
mal condition and as a function of the flood losses and therefore were
le s s mobile . Other po s sibilitie s, of cour s e, exi st.
An analysis of the reasons for respondents' lack of availa-
bility reveals no consistent trends. In a few cases, the respondent
was unknown, either because he had moved since the directory had
been prepared and was therefore unknown to the new tenant, or the
directory was in error. A few had been drafted, or had recently mar-
ried and were no longer living in Port Jervis. One was a mental case
and another did not speak English. A few railroad men were away on
their jobs. A few people were out of town on vacation or business.
Finally, some were not available after as many as six call-backs for
unknown reasons.
F. Additional Factors Considered
.
During the planning phase of this study, the investigators
seriously considered the po s sibility of contacting re spondents by tele -
phone before the interview. It was hoped that making an appointment
would simplify the task of the interviewer, cut down the number of
call-backs, etc. This plan was abandoned because many of the
96
OCR for page 97
respondents did not have telephones. Those who were telephone sub-
scribers could, of course, have been called. However, if all individu-
als having telephones had been contacted or forewarned, while those
not having telephones had received no notification, we might have
introduced a systematic error into our data-collection procedures.
The extent of this error would have been impossible to deter-
mine. When cloaking socio-economic comparisons, we might have
found marked differences in the responses of upper versus lower-
clas s re spondents . Lower - clas s individuals are generally tho s e who
do not have telephones, so that differences observed in the responses
might have been attributable to the forewarning rather than to socio-
e cono colic factor s.
A previous study by Nuckols (15) involving the forewarning
of respondents indicated that this had no effect upon the responses of
the members of a sample. However, this survey dealt with materi-
als which involved little or no defensiveness or ego-involvement. In
addition, the forewarning was clone through the mail. The investi-
gators felt that it would have been extremely unwise to attempt to
generalize from this one quite different study, ant] so clecidecl not to
forewarn respondents.
G. Empirical Checks
Although our sampling technique s are de signed to maximize
the probability of representativeness, it is still incumbent upon the
investigator to offer evidence to support his contention that the sample
is representative. In the usual market or opinion study, comparisons
of the demographic characteristics of the sample and census data are
frequently made. However, following a disaster, the mortality,
hospitalization, or movement (to endamaged or healthier areas) of
inhabitants may leave a study population whose demographic character-
istics are no longer congruent with those originally surveyed] in the
Census. Moreover, Census data becomes rapidly outdated in our
mobile society.
It seems, therefore, that investigators should run checks on
the internal consistency of the data as a measure of reliability, and
should also check the validity of respondent reports by comparing
97
OCR for page 98
them with known facts concerning the times, places, and occurrences
of various events during the disaster. Some major examples of em-
pirical checks on the respondent data in this study are given below.
The reader will note other such checks in the body of the report.
The sample contains too large a proportion of women (59. 8
per cent) because of difficulties encountered by interviewers in trying
to contact male respondents. In most other respects, the sample
seems to be representative of the Port Jervis population. (See also
page 23. ~
When the sample is divided into two groups according to geo-
graphical location within the city, we find that the discrepancy between
the groups in educational level and in socio-economic status is con-
sistent with what we know about neighborhoods in the community.
The behavior of the sample conforms to that which would be
predicted from the descriptions of officials who were at the scene of
the disaster. The official report of the Police Chief estimated that
between 2, 500 and 3, 000 persons evacuated as a result of the false
report. When the number evacuating is estimated from the sample
data, the range is the same.
Information from the key interviews leacis us to believe that
the fire-truck which disseminates} the rumor was broadcasting for a
few minutes around 11:15 that night. Eleven-thirty p. m. is the median
time indUcated by respondents for receipt of the false report. Resi-
dents in the flooded area, in which that fire-truck was broadcasting,
are Dose who report hearing the threat from an official source.
We also know from the reports of Police, Fire Department,
and the local radio station, WDLC, the time and contents of the denial
me s sage s which the se agencie s broadcast. The re spondent data are
accurate with respect to this information in at least the following ways:
At approximately ~ 1: 3 0 - 1 1: 45, official center s were attempt-
ing to verify Me report. At this time, the fire -truck loudspeaker s
gave a short public message which, in effect, told people that an at-
tempt to verify was in progress, and that they thought the report was
false. Only a few minutes later, denial was received from officials
at Wallenpaupack Dam, ant] a le s s ambiguous `~'e s sage was s ent out.
98
OCR for page 99
Whenever respondents reported hearing this ambiguous message, it
was invariably reported as the first denial message they heard.
11:40 and 12:30
The fire-truck loudspeakers broadcast the denial between
Fire-truck messages tend to be reported as first
and second messages received. On the other hand, the radio station
did not go back on the air until 12:10 that night. Radio messages tend
to be reported as second and third messages. Despite the fact that
the total number of messages decreases between first and second
denials heard, the total number of radio messages increases.
Our empirical checks, therefore, indicate that the sample
is representative with respect to: education, socio-economic status,
flight, rumor dissemination, and denial dissemination. Only with
regard to sex distribution did we find evidence of non-representative-
ness.
99
OCR for page 100
KEY RESPONDENTS
1. Police Department
a. Chief
b. Radio dispatcher
2. Civil Defense
a. Director
b. Relief Director
c. Radio op erato r
3. Sparrowbush Fire Department
a. Chief
b. Captain
c. Radio operator
d.
Volunteer fireman involved in spread of rumor
4. Port Jervis Fire Department
a. Chief
b. Chief radio operator
Assistant radio operator
5. WDLC - local radio broadcasting company
a. Program Director
b. Two announcers
6. Newspaper - Union Gazette
a. Editor
b. City Editor
Publi she r
7 . Other Po rt Je rvi s Official s
~ . . ~ . _
a. Mayor
b. Alderman
8. Others in Communication Centers
a. Manager of the telephone company
b. A local ham radio operator
c. Erie Railroad communication center
9. Other individuals in important community positions
a. Director of a light and power company
b. Priest in a Port Jervis church
Di r e c for of a P art Je rvi s ho spital
d. A ho spital doctor and nur s e s
e. YMCA night clerk
f. Manager of a Port Jervis the atre
Bartencler at a Port Jervis hotel
100
3 operators
Representative terms from entire chapter:
alphabetical list
