AP Statistics Inference for Regression

Data was collected on the weight of a male  laboratory rat for the first 25 weeks after its birth. The linear regression equation is 
y= 40x+100, where x is number of weeks and y is weight in grams. 
What does the y-intercept mean in context of the problem?

• The predicted weight of the rat in year 0. 
• The predicted weight of the rat at birth. 
• The current weight of the rat. 
• The average increase in the rat's weight. 

The residual plots from five different least squares regression lines are shown below. Which of the plots shows the strongest evidence that its regression line is an appropriate model for the data and is consistent with the assumptions required for inference for regression?

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The equation of the least squares regression line for a set of data is y=0.68+1.21x. What is the residual for the point (3, 4)?

• -0.31

• -0.68

• -1.52

• -3.63

• -4.31

The computer output below shows the result of a linear regression analysis for predicting the concentration of zinc, in parts per million (ppm), from the concentration of lead, in ppm, found in fish from a certain river. Which of the following statements is a correct interpretation of the value 19.0 in the output?

• On average there is a predicted increase of 19.0 ppm in concentration of lead for every increase of 1 ppm in concentration of zinc found in the fish.

• On average there is a predicted increase of 19.0 ppm in concentration of zinc for every increase of 1 ppm in concentration of lead found in the fish.

• The predicted concentration of zinc is 19.0 ppm in fish with no concentration of lead.

• The predicted concentration of lead is 19.0 ppm in fish with no concentration of zinc.

• Approximately 19% of the variability in the zinc concentration is predicted by its linear relationship with lead concentration.

Which of the following pairs of variables would be expected to have a negative association?

• GPA and height

• Number of chores and weekly allowance

• Number of hours spent studying and test grade

• Number of miles driven and amount of gas remaining in gas tank

• Age and IQ

There is a linear relationship between the amount of fat in a sandwich and the amount of calories in a sandwich. A least squares line was fit using some data collected by nutritionists, resulting in the equation y=217.3+35.2xwhere x is fat grams and y is caloric content. What is the estimated caloric content of a sandwich with 8 grams of fat?

• 35.2 calories

• 217.3 calories

• 281.6 calories

• 498.9 calories

• 1738.4 calories

Which of the following scatter plots could have created the residual plot below?

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True or False:

If the residual plot has a pattern then a linear regression model IS appropriate.

• True

• False

How do you find the residual?

• predicted value - actual value

• actual value - predicted value

• what values are you talking about?

The correlation coefficient measures...

• whether there is a relationship between two variables.
• the strength of the relationship between two quantitative variables.
• whether a cause and effect relation exists between two variables.
• the strength of the linear relationship between two quantitative variables.