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Chapter 12: Q.1.3 (page 777)
Use this linear model to predict the U.S. population in . Show your work.
The regression line,.
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In the casting of metal parts, molten metal flows through a 鈥済ate鈥� into a die that shapes the part. The gate velocity (the speed at which metal is forced through the gate) plays a critical role in die casting. A firm that casts cylindrical aluminium pistons examined a random sample of pistons formed from the same alloy of metal. What is the relationship between the cylinder wall thickness (inches) and the gate velocity (feet per second) chosen by the skilled workers who do the casting? If there is a clear pattern, it can be used to direct new workers or to automate the process. A scatterplot of the data is shown below
A least-squares regression analysis was performed on the data. Some computer output and a residual plot are shown below. A Normal probability plot of the residuals (not shown) is roughly linear.
Do these data provide convincing evidence of a straight-line relationship between thickness and gate velocity in the population of pistons formed from this alloy of metal? Carry out an appropriate significance test at the level.
Random assignment is part of a well-designed comparative experiment because
(a) It is more fair to the subjects.
(b) It helps create roughly equivalent groups before treatments are imposed on the subjects.
(c) It allows researchers to generalize the results of their experiment to a larger population.
(d) It helps eliminate any possibility of bias in the experiment.
(e) It prevents the placebo effect from occurring
Park rangers are interested in estimating the weight of the bears that inhabit their state. The rangers have data
on weight (in pounds) and neck girth (distance around the neck in inches) for 10 randomly selected bears. Some
regression output for these data is shown below.
Which of the following represents a 95% confidence interval for the true slope of the least-squares regression line relating the weight of a bear and its neck girth?
The professor swims Here are data on the time (in minutes) Professor Moore takes to swim 2000 yards and his pulse rate (beats per minute) after swimming for a random sample of 23 days:
(a) Is there statistically significant evidence of a negative linear relationship between Professor Moore's swim time and his pulse rate in the population of days on which he swims 2000 yards?
Carry out an appropriate significance test at the level.
(b) Calculate and interpret a confidence interval for the slope of the population regression line.
Color words Do the data provide evidence of a difference in the average time required to perform the two tasks? Include an appropriate graph and numerical summaries in your answer.
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