According to the National Center for Health Statistics, the distribution of height for 16-year-old females is modeled well by a Normal density curve with mean μ = 64 inches and standard deviation o = 2.5 inches. Assume this claim is true for the three hundred 16-year-old females at a large high school. Which of the following describes the distribution of the population of all girls at this high school?

Suppose the flow of current (milliamps) in wire strips of a certain type under specified conditions can be modeled with a normal distribution having mu (mean) = 20 and sigma (SD) = 1 (hint: think about how the corresponding density curve relates to the standard normal curve). What proportion of strips will have of between 18.5 and 22 milliamps?

Researchers wanted to determine if carpeted rooms contained more bacteria than uncarpeted rooms. To determine the amount of bacteria in a room, researchers pumped the air from the room over a Petri dish at the rate of 1 cubic foot per minute for eight carpeted rooms and eight uncarpeted rooms. Colonies of bacteria were allowed to form in the 16 Petri dishes. The results are given in the table below. Assume the distribution to be approximately normal. Do carpeted rooms have more bacteria than uncarpeted rooms?   Carpeted Rooms Uncarpeted Rooms 11.7 12.0 8.2 8.3 7.1 3.8 13.1 7.3 10.6 12.0 10.1 11.1 14.8 10.3 14.0 13.7   What is the critical value(s) for this hypothesis test if group 1 is the carpeted rooms and group 2 is the uncarpeted rooms. 1.895 2.306 2.365 1.833 1.860

Suppose that Melanie is a researcher who wishes to estimate the mean birthweight of full-term babies in her hospital. What is the minimum number of babies should she sample if she wishes to be at least 90% confident that the mean birthweight of the sample is within 225 grams of the the mean birthweight of all babies? Assume that the distribution of birthweights at her hospital is normal with a standard deviation of 600 g.

What is the difference between the t and z distributions? Which is used more in biological research? Explain your anwser.