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Unformatted text preview: 5E Final practice Formulas at end are as they will be on exam. For any hypothesis test, clearly state null and alternative hypotheses. 1. Suppose two variables x and y have a negative correlation and follow the regression model y = 2- . 1 x + , where is normal with a standard deviation of .7. We do a least-squares regression using 30 values for x , where the values have a mean of 4 and a sample standard deviation of 1.2. What is the probability that we get a positive slope in our regression analysis? What if we use 100 values for x , with the same mean and standard deviation them? What if the standard deviation of is only .4? Hint: Use 12.17 from p. 513. To do that use the sample st dev to find ( x i- x ) 2 . 2. Below is a scatter plot of data with regression output: b = 5 . 1, b 1 = 4 . 7 and SSE = 345. The sample standard deviation of the x values are 12.3 and the mean is 5.5. The sample standard deviation of the y values are 3.4 and the mean is 10.1. There are 30 data points plotted. Find a 95% confindence interval for the the slope b 1 . At a 5% significance level, does the data provide evidence that there is a correlation between the variables? Find a 95% confidence interval for the mean of y given that x is equal to 7. Find a 95% confidence interval for an individual valueequal to 7....
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- Fall '08