As part of Pew Research Center Poll, subjects were asked if there is solid evidence that earth is getting warmer. Among 1501 respondents, 20% said that there isn't such evidence. Employ a 0.01 significance level to test claim that less than 25% of population thinks that there is not solid evidence that the earth is getting warmer.
Determine the test statistic. Is it a t-statistic or a z-statistic?