1. Students often incorrectly believe that inference for a population proportion based on the sample proportion is always valid if n > 30. They are confusing a general rule of thumb for the Central Limit Theorem which says that as the sample size, n, gets large becomes Normally distributed with a different rule for proportions. The correct rule for proportions is that we can create confidence intervals for p based on if
A. n is at least 10.
B. there are at least 15 successes and 15 failures.
C. np = 5 and n(1 - p) = 5.
2. A sample of 75 students found that 55 of them had cell phones. The margin of error for a 95% confidence interval estimate for the proportion of all students with cell phones is
A. 0.084.
B. (0.633, 0.833).
C. 0.100.