Chapter 12, Problem 12.45AC

Suppose IQ scores were obtained for 20 randomly selected sets of twins. The 20 pairs of measurements yield x= 106.07, y = 105.75, r= 0.888, P-value = 0.000, and y = - 12.86 + 1.12x, where x represents the %D %3D IQ score of the twin born second. Find the best predicted value of y given that the twin born second has an IQ of 92? Use a significance level of 0.05. Click the icon to view the critical values of the Pearson correlation coefficient r. The best predicted value of y is (Round to two decimal places as needed.)

A scientist wants to establish if the Mississippi’s river height has increased using data from 1970 and 2020. Historically, it’s known that the variance of the height within any given year is 4.5ft. The sample from 1970 has 80 measurements with ?1μ1 = 30ft and the sample from 2020 has 260 measurements  with ?2μ2 = 31.5ft. Find a 95% confidence interval for the average increase of height.

Anagha is interested in buying a new Model X car and wants to gather information about how the selling price of the car is related to the year of the model. She randomly selects 24 used Model X cars for sale. For each used car, she records the car’s selling price (in dollars) and age (in years). She computes a 96 percent confidence interval to estimate the slope of the regression line relating the age of a used Model X car to its selling price. The resulting confidence interval is given by (−5,556,−3,157). Assume that the conditions for inference on the slope of the regression equation are met. Which of the following is the correct interpretation of the confidence interval?     We are 96 percent confident that a Model X car will have a predicted decrease in selling price of between $3,157 and $5,556. A Ninety-six percent of the time, a one-year increase in the age of a Model X car will result in a predicted decrease in selling price of between $3,157 and $5,556. B…