Suppose that the length of long-distance phone calls, measured in minutes, is known to have an exponential distribution with the average length of a call equal to eight minutes. a. Define the random variable. X = b. Is X continuous or discrete? с. X~ d. μ . e. o =

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Is the following random variable discrete or continuous? Let X represent the number of books in a random professor's office.

1.  Let XX represent the full height of a certain species of tree. Assume that XX has a normal probability distribution with a mean of 231.1 ft and a standard deviation of 5.6 ft.A tree of this type grows in my backyard, and it stands 230 feet tall. Find the probability that the height of a randomly selected tree is as tall as mine or shorter.P(X<230) =  Enter your answer accurate to 4 decimal places.   2.  Assume that z-scores are normally distributed with a mean of 0 and a standard deviation of 1.If P(−0.7<z<b)=0.7352P find b.b= (Round to two decimal places.) Do not round until the very last step. Any intermediate steps should include all decimal places.

4. As fallen trees lie on the forest floor they slowly decay. Will the amount of light present have an impact on the rate of decay? In the following table x is a random variable representing the remaining percentage of total mass of a log after it was exposed to the elements for three weeks while y represents the numbers of hours of direct sunlight the log received each day. X 0.60 .70 .65 .82 .87 y 1.0 2.3 3.0 4.0 4.5 (a) Plot a scatter diagram of the data. Remember to label your axes appropriately and choose a consistent scale. (b) Based on a scatter diagram, would you estimate the correlation coefficient to be positive, close to zero, or negative? Please circle one of the following choices: A. Positive B. Close to zero C. Negative (c) Interpret your results from parts (a) and (b). 16 tv