Google Surveys automatically analyzes your results. If you click 
If the system has 95% confidence in the winning answer, you see "Winner is statistically significant." Your results are statistically significant if running this question again would result in the same winning answer 95% of the time.
We determine 95% confidence in the winning answer by running up to 10,000 simulations that sample from the Gamma distribution. We stop the simulations when one answer has won 95% of the time for at least 250 simulations. If there is no winning answer after 10,000 simulations, we say that the confidence is too close to call.
If there is less than 95% confidence in the winning answer, you see “Confidence too close to call.” More responses are needed before the winner can be determined with statistical significance.