The study described in this publication was based on a representative sample of the adult (eighteen years and above) Jewish population of Israel. The sample size of the survey was set at 600 respondents. Using a stratified random sampling procedure, the questionnaire was administered by trained interviewers (from a pool of 80 trained face to face interviewers) to 632 respondents in the early months of 2012 (from late February to mid April).
The interviews were conducted at the permanent residence of the respondents and each interview lasted approximately one hour. Each household was visited at least three times to increase the response rate and decrease the number of refusals. At each household, one adult (over the age of eighteen) was interviewed. All told, 1238 households were selected. The overall response rate was thus 51 percent (632 out of 1238). However, of the 1238 households, 27 were unpopulated/offices and 105 were made up of people who could not communicate in Hebrew. Subtracting these households, which are irrelevant for the study population, the response rate is 57 percent (632 out of 1106). Of the 1106 relevant households, 90 were either empty (on all three visits), or were households where the respondent was ill or abroad.
Thus, of the 1016 households that were visited, 632 participated in the study while 384 refused to participate. The effective response rate is, therefore, 62 percent and the refusal rate is 38 percent. This is far better than telephone surveys, where the response rate in many cases is less than 50 percent and in some surveys the refusal rate is over two thirds. Our research design, based on face to face interviews, minimized the self-selection bias that stems from possible differences between those willing and those refusing to participate in the study.
Units of analysis (households) were chosen by a two-stage random sampling procedure that included the stratification of geographic areas and a construction of representative statistical areas. The households were drawn from 58 statistical areas, chosen randomly and spread over 38 different localities – 26 cities and large towns and 12 kibbutzim and other smaller communities. Each statistical area was constructed as a representative segment of the overall socio-demographic composition typical for that area.
The sampling error is 4 percent.
In order to check whether the sample is indeed representative of the adult Israeli Jewish population, the results for several demographic indicators were compared with nationwide data reported by the Central Bureau of Statistics (CBS). Table A1 shows the distribution according to gender, as reported by the CBS, for the entire Jewish population eighteen years and older, and as found in the 2012 sample. The distribution for 2012 is similar to the data provided by the CBS for 2010; the differences are small and all well within the sampling error.
Table A1. CBS Jewish population in 2010 and INSS survey distribution by gender
Gender CBS data, 2010
% Sample, 2012
%
Men 49.2 48.4
Women 50.8 51.6
Total 100 100
Table A2 presents the distribution for age. As can be seen there is a clear similarity between the 2012 sample and the CBS data. For seven of the nine age groups, differences are minimal, if they exist at all, and are all well within the sampling error. In two instances only, namely the age groups of 20-24 and 65-74, is there a meaningful discrepancy; the 20-24 age group is underrepresented in the INSS survey by 4 percent and the 65-74 age group is overrepresented in the INSS survey by 5 percent (only slightly above the sampling error). Increasing the number of categories within a given variable increases the sensitivity of a variable but also raises the probability of a sampling error for any given category. Thus, if age were divided into three categories (instead of nine), namely young (18-29), adult (30-64), and senior
The Voice of the People: Israeli Public Opinion on National Security 2012
I
111citizens (65 and above), the differences between the CBS data and that of the sample (1-3 percent) would all be within the sampling error.
Table A2. CBS Jewish population in 2010 and INSS survey distribution by age groups
Age groups CBS data, 2010
% Sample, 2012
%
18-19 4 4
20-24 11 7
25-29 11 13
30-34 10 10
35-44 17 17
45-54 16 14
55-64 15 16
65-74 8 13
75+ 8 6
Total 100 100
Tables A3 and A4 present the distribution for two key demographic variables: education measured in years of schooling and country of origin.
Table A3. CBS Jewish population in 2010 and INSS survey distribution by education
Years of Schooling CBS data, 2010
% Sample, 2012
%
0 2 1
1-4 1 1
5-8 5 5
9-10 6 3
11-12 35 38
13-15 26. 23
16+ 25 29
Total 100 100
Table A4. CBS Jewish population in 2010 and INSS survey distribution by geographic origin
Origin CBS data, 2010
% Sample, 2012
% Father born in Israel, respondent born in
Israel 22 25
Respondent born in Europe, US (Western,
Central, Eastern, USSR) 26 23
Respondent born in Asia and Africa
(including USSR) 13 13
Respondent born in Israel, father born in
Asia and Africa 24 24
Respondent born in Israel, father born
Europe, US 15 15
Total 100 100
Comparison of the sample with the CBS data suggests that overall the sample is representative of the general adult Jewish population. Regarding education, all the discrepancies are within the sampling error, with the only meaningful discrepancy in the 16+ category. Here too, if we divide education into three categories (instead of seven), namely less than high school, high school, and post-high school education (for the most part academic), the differences are 0-1 percent, in effect nonexistent. Regarding the country of origin of the respondents, there is almost perfect similarity between the INSS sample and the CBS data. For three of the groups, the numbers are identical, and for the remaining two groups the discrepancy for each group is 3 percent, i.e., within the sampling error.
As demonstrated throughout this monograph, religious identification is the single most influential factor in determining attitudes and opinions on national security issues. Indeed, the weight of this factor in determining one’s opinions is equal or even greater than that of all other demographic variables combined. It is therefore essential to examine whether the distribution on this key variable in our sample is equivalent to the distribution for the entire population. In 2010, as part of a nationwide social survey conducted by the CBS on a sample of 7,000 respondents representing the entire adult population of twenty years and older, the CBS gathered data as to one’s religious self-identification. Table A5 presents the distribution on religious self-identification as reported by the CBS in 2010 and responses to an identical question for the sample.
The Voice of the People: Israeli Public Opinion on National Security 2012
I
113Table A5. CBS Jewish population in 2010 and INSS survey distribution by religious self-identification
Religious affiliation CBS data, 2010
% Sample, 2012
%
Ultra-Orthodox 9 9
Religious 10 13
Traditional 38. 32
Secular 43 46
Total 100 100
The main difference is in the traditional group. This group is underrepresented by 6 percent, which is evenly divided between the religious group, which is overrepresented by 3 percent and the secular group which is also overrepresented by 3 percent. The difference for these two groups is within the sampling error; the representation of the ultra-Orthodox is identical with that reported by the CBS. For most items, the traditional group is in the middle; the religious group is to the right and the secular group to the left. Thus, the fact that the religious group and the secular group are each overrepresented by 3 percent balances each other and neutralizes the underrepresentation of the traditional group.
Taken as a whole, the sample of the Jewish adult population of Israel drawn for the INSS survey in 2012 constitutes a representative sample of the population and the analysis of the sample data can be safely used to infer conclusions about this population.