There are 120 children at a school assembly. 15 are 3rd graders; 45 are 4th graders; and 60 are 5th graders. Each student has entered their name in a drawing for a prize. What is the probability that the winner will be a 3rd grade student?

Twelve different video games showing substance use were observed and the duration times of game play (in seconds) are listed below. the design of the study justifies the assumption that the sample can be treated as a simple random sample. use the data to construct a 99% confidence interval estimate of μ, the mean duration of game play. 4028 4316 4816 4650 4036 5010 4833 4331 4307