Chapter 6: Q.33 (page 357)
Predicting posttest scores() What is the equation of the linear regression model relating posttest and pretest scores? De铿乶e any variables used.
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Chapter 6: Q.33 (page 357)
Predicting posttest scores() What is the equation of the linear regression model relating posttest and pretest scores? De铿乶e any variables used.
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For each of the following situations, determine whether the given random variable has a binomial distribution. Justify your answer.
Choose three students at random from your class. Let the number who are over feet tall.
Buying stock You purchase a hot stock for . The stock either gains or loses each day, each with probability . Its returns on consecutive days are independent of each other. You plan to sell the stock after two days.
(a) What are the possible values of the stock after two days, and what is the probability for each value? What is the probability that the stock is worth more after two days than the you paid for it?
(b) What is the mean value of the stock after two days?
(Comment: You see that these two criteria give different answers to the question "Should I invest?")
North Carolina State University posts the grade distributions for its courses online.Students in Statistics in a recent semester received As, Bs, Cs, Ds, and Fs. Choose a Statistics student at random. The student鈥檚 grade on a four-point scale (with ) is a discrete random variable X with this probability distribution:

Say in words what the meaning of is. What is this probability?
45. Too cool at the cabin? During the winter months, the temperatures at the Stameses' Colorado cabin can stay well below freezing or for weeks at a time. To prevent the pipes from freezing, Mrs. Stames sets the thermostat at . She also buys a digital thermometer that records the indoor temperature each night at midnight. Unfortunately, the thermometer is programmed to measure the temperature in degrees Celsius. Based on several years' worth of data, the temperature in the cabin at midnight on a randomly selected night follows a Normal distribution with mean and standard deviation.
(a) Let the temperature in the cabin at midnight on a randomly selected night in degrees Fahrenheit (recall that . Find the mean and standard deviation of .
(b) Find the probability that the midnight temperature in the cabin is below . Show your work.
85. Aircraft engines Engineers define reliability as the probability that an item will perform its function under specific conditions for a specific period of time. A certain model of aircraft engine is designed so that each engine has probability of performing properly for an hour of flight. Company engineers test an SRS of engines of this model. Let the number that operate for an hour without failure.
(a) Explain why is a binomial random variable.
(b) Find the mean and standard deviation of. Interpret each value in context.
(c) Two engines failed the test. Are you convinced that this model of engine is less reliable than it鈥檚 supposed to be? Compute and use the result to justify your answer.
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