Abstract
Each month since 1994, JNN (Japan News Network) has conducted a nationwide public opinion survey on cabinet support and political party support, employing two different methods, the face-to-face interview survey and the telephone survey. This paper presents a comparison of the results derived from these two different suevey methods. The comparisons are made taking the following into consideration: the support rates of the present cabinet, the Liberal Democratic Party and the Democratic Party of Japan as well as the rate of the non-committed for each month.
Our comparisons have found that there are, in fact, very large differences between the results in the interview surveys and those in the telephone surveys in the cases of both the support rates for the present cabinet and the rates of the non-committed for each time period. This indicates that different methods could cause different results even when we ask the same questions.
On the other hand, when we see these results as time series data, we find a very high correlation (0.95) between the results of the two methods in the case of the rate of present cabinet support.
However, in the other cases, the correlations are not as high as those of present cabinet support, and the size of the correlations seems to depend on the nature (e.g., the simplicity) of the questions.
