The researchers designed an online survey to administer among a carefully screened sample of 2,545 English adults ages 18 and older who are nationally representative by age, gender, region and socioeconomic grade. The sample error on this survey is plus or minus 1.9% points at the 95% confidence level. Additional data were collected through an online survey among an oversample of 1,592 English practising Christians. The sample error on the oversample data is plus or minus 2.5% points at the 95% confidence level.The results of their research can be found here.
The table below show the responses for the question: 'When you consider the factors that positively influenced you to become a Christian, which two or three of the following, if any, had the most impact?'