Sampling Pentecostals . Pentecostals are among the fastest-growing Christian groups in many countries. The Pew Forum on Religion and Public Life surveyed Pentecostal Christians in 10 countries and compared their opinions with those of the general population. In South Korea, random samples by Gallup Korea had margins of error (we will give more detail in later chapters) of ±4% for the general public and 9% for Pentecostals. What do you think explains the fact that estimates for Pentecostals were less precise?