Exam 8: Regression, Associations, and Predictive Modeling

A pharmaceutical company investigating whether drug stores are less likely than food markets to Remove over-the-counter drugs from the shelves when the drugs are past the expiration date Found a P-value of 2.8%. This means that:

Was your test one-tail upper tail, lower tail, or two-tail? Explain why you chose that kind of test in this situation.

High Score The longer you play a video game, the higher score you can usually achieve. An analysis of a popular game found the following relationship between the hours a player has played a game and their corresponding high score on that game. Dependent variable is High Score R-squared $= 76.5 \%$ $s = 383.3$ with 89 degrees of freedom Variable Coefficient s.e. of Coeff Constant 524.8 145.3 Hours 2498.8 324.5 a. Write the regression equation and define the variables of your equation in context. b. Interpret the slope in context. c. Interpret the y-intercept in context. d. Interpret s in context. e. What is the correlation coefficient? Interpret this value in context.

According to the National Telecommunication and Information Administration, 50.5% of U.S. Households had Internet access in 2001. What is the probability that four randomly selected U.S. Households all had Internet access in 2001?

Name the sampling strategy in each plan.

To check the effect of cold temperatures on the battery's ability to start a car researchers purchased A battery from Sears and one from NAPA. They disabled a car so it would not start, put the car in a Warm garage, and installed the Sears battery. They tried to start the car repeatedly, keeping track of The total time that elapsed before the battery could no longer turn the engine over. Then they Moved the car outdoors where the temperature was below zero. After the car had chilled there for Several hours the researchers installed the NAPA battery and repeated the test. Is this a good Experimental design?

Cool Off A survey of southern California houses in a given town shows that 70% of the homes have an air conditioning system and 90% of home have at least one ceiling fan. 65% of all homes surveyed had both features. a. What is the probability that a randomly selected home neither feature? b. What is the probability that a randomly selected home has a ceiling fan, given that it already has an air conditioning system? c. Do these two house features appear to be independent? Justify your answer.

Assuming the pet store owner is correct in thinking that only 4% of her customers purchase specialty clothes for their pets, how many customers should she expect before someone buys a garment for their pet?

Which of these random variables has a geometric model?

Use your equation to predict the cost of a 48" stop sign.

If $r = - 0.4$ for the relationship between the time of day and amount of coffee in an office worker's mug, which are true? I. $r ^ { 2 } = - 16 \%$ II. There is a linear relationship between time and amount of coffee. III. $16 \%$ of the variability is correctly predicted by time of day.

We are about to test a hypothesis using data from a well-designed study. Which is true? I. A large P-value would be strong evidence against the null hypothesis. II. We can set a higher standard of proof by choosing α = 10% instead of 5%. III. If we reduce the risk of committing a Type I error, then the risk of a Type II error will also Decrease.

One administrator suggested walking into the break room and testing the people in there. What type of sampling would this be? Explain why this method is biased. Be sure to name the kind(s) of bias you describe and link it to the variable of interest.

The Y-variable in a regression analysis is also known as the...

A company's manufacturing process uses 500 gallons of water at a time. A "scrubbing" machine then removes most of a chemical pollutant before pumping the water into a nearby lake. Legally the treated water should contain no more than 80 parts per million of the chemical, but the machine isn't perfect and it is costly to operate. Since there's a fine if the discharged water exceeds the legal maximum, the company sets the machine to attain an average of 75 ppm for the batches of water treated. They believe the machine's output can be described by a Normal model with standard deviation 4.2 ppm. (SHOW WORK) a. What percent of the batches of water discharged exceed the 80ppm standard? b. The company's lawyers insist that they not have more than 2% of the water over the limit. To what mean value should the company set the scrubbing machine? Assume the standard deviation does not change. c. Because achieving a mean that low would raise the costs too much, they decide to leave the mean set at 75 ppm and try to reduce the standard deviation to achieve the "only 2% over" goal. Find the new standard deviation needed. d. Explain what achieving a smaller standard deviation means in this context.

The price of first class stamp has followed inflation over time and has increased at a constant Percentage over time. The most useful predictive model is probably…

If Jacob removes 3 marbles from the bag, what are the chances that he will get at least one orange?

Cloning A random sample of 800 adults was asked the following question: "Do you think current laws concerning the use of cloning for medical research are too strict, too lenient, or about right?" The pollsters also classified the respondents with respect to highest education level attained: high school, 2- year college degree, 4-year degree, or advanced degree. We wish to know if attitudes on cloning are related to education level. (All the conditions are satisfied - don't worry about checking them.) . a. Write appropriate hypotheses. b. Suppose the expected counts had not been given. Show how to calculate the expected count in the first cell (106.01). c. How many degrees of freedom? Explain. d. State your complete conclusion in context.

The two samples whose statistics are given in the table thought to come from populations with Equal variances. What is the pooled estimate of the population standard deviation? Mean SD 50 22 3 55 25 4

A biology professor responds to some student questions by e-mail. The probability model below describes the number of e-mails that the professor may receive from students during a day. e-mails received 0 1 2 3 4 5 Probability 0.05 0.10 0.20 0.25 0.30 0.10 a. How many e-mails should the professor expect to receive each day? b. What is the standard deviation? c. If it takes the professor an average of ten minutes to respond to each e-mail, how much time should the professor expect to spend responding to student e-mails each day?