Which of the following is not one of the conditions that must be satisfied in order to perform inference about the slope of a least-squares regression line? (a) For each value of x, the population of y-values is Normally distributed.
Oil and residuals Exercise 59 on page 193 (Chapter 3) examined data on the depth of small defects in the Trans-Alaska Oil Pipeline. Researchers compared the results of measurements on 100 defects made in the field with measurements of the same defects made in the laboratory. The figure below shows a residual plot for the least-squares regression line based on these data. Are the conditions for performing inference about the slopeβ of the population regression line met? Justify your answer.
A major agricultural company is testing a newvariety of wheat to determine whether it is more resistant tocertain insects than is the current wheat variety. The pro-portion of a current wheat crop lost to insects is 4%. Thus,the company wishes to test the following hypotheses:
In the casting of metal parts, molten metal flows through a “gate” 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 aluminum pistons examined a random sample of 12pistons 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 automate the process. A scatterplot of the data is shown below.
Ideal proportions The students in Mr. Shenk's class measured the arm spans and heights (in inches) of a random sample of 18 students from their large high school. Some computer output from a least-squares regression analysis on these data is shown below. Construct and interpret a 90% confidence interval for the slope of the population regression line. Assume that the conditions for performing inference are met.
We record data on the population of a particular country from 1960to 2010. A scatterplot reveals a clear curved relationship between population and year. However, a different scatterplot reveals a strong linear relationship between the logarithm (base 10) of the population and the year. The least-squares regression line for the transformed data is,
Growth hormones are often used to increase the weight gain of chickens. In an experiment using 15chickens, five different doses of growth hormone (0, 0.2, 0.4, 0.8, and 1.0milligrams) were injected into chickens (3chickens were randomly assigned to each dose), and the subsequent weight gain (in ounces) was recorded. A researcher plots the data and finds that a linear relationship appears to hold. Computer output from a least-squares regression analysis for these data is shown belo
A survey ﬁrm wants to ask a random sample of adults in Ohio if they support an increase in the state sales tax from 5%% to 6%, with the additional revenue going to education. Let p^denote the proportion in the sample who say that they support the increase. Suppose that 40%of all adults in Ohio support the increase. How large a sample would be needed to guarantee that the standard deviation of p^is no more than 0.01
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