In a recent study on world happiness, participants were asked to evaluate their current lives on a scale from 0 to 10, where 0 represents the worst possible life and 10 represents the best possible life. The responses were normally distributed, with a mean of 6.1 and a standard deviation of 2.4. Answer parts (a)-(d) below. ... (a) Find the probability that a randomly selected study participant's response was less than 4. The probability that a randomly selected study participant's response was less than 4 is 0.1907. (Round to four decimal places as needed.) (b) Find the probability that a randomly selected study participant's response was between 4 and 6. The probability that a randomly selected study participant's response was between 4 and 6 is (Round to four decimal places as needed.)

Because of the popularity of movies as an entertainment medium for college students, you plan to do a national study of the average cost of a movie ticket. If you assume that σ=$0.50, what sample size would you have to take to be 95% confident that your estimate was within $0.25 of the true mean ticket prices

A racing car consumes a mean of 103 gallons of gas per race with a variance of 36. If 38 racing cars are randomly selected, what is the probability that the sample mean would be greater than 101.5 gallons? Round your answer to four decimal places.

(a) The population 3, 4, 9, 14, and 20 has a mean of 10 and a standard deviation of 6.356. The z-scores for each of the five data values are  z3 ≈ −1.101, z4 ≈ −0.944, z9 ≈ −0.157, z14 ≈ 0.629, and z20 ≈ 1.573.  Find the mean and the standard deviation of these z-scores. mean       standard deviation   (b) The population 2, 6, 12, 17, 22, and 25 has a mean of 14 and a standard deviation of 8.226. The z-scores for each of the six data values are  z2 ≈ −1.459, z6 ≈ −0.973, z12 ≈ −0.243, z17 ≈ 0.365, z22 ≈ 0.973, and z25 ≈ 1.337.  Find the mean and the standard deviation of these z-scores. mean       standard deviation       (c) Use the results of part (a) and part (b) to make a conjecture about the mean and standard deviation of the z-scores for any set of data. The mean of the z-scores is always 1, and their standard deviation is 0. The mean of the z-scores is always 1 more than the standard deviation.     The mean and standard deviation of z-scores are never the same.…