Select the correct answer from each drop-down menu. Tomás is gathering data about the sleeping habits of high school students. So far, he has completed 3 different surveys, each with 70 respondents. What should Tomás expect as he continues his data-gathering process? As the number of surveys increases, the mean of the sample means will approach _________, and the means will be _________.
a. the population mean, less variable
b. the population mean, more variable
c. the sample mean, less variable
d. the sample mean, more variable