Things to Know for Test

Chapter 3-4 ReviewName______

Things to Know for Test:

• r is correlation. Correlation is a measure of strength of linear data.
• r2 is the percent of variation in ‘y’ that can be explained by ‘x’.
• You predict a ‘y’ value by plugging in your given ‘x’ value.
• Residuals are , or actual y – predicted y
• A residual plot tells you if your model is an appropriate fit! You want scatter!
• To draw an EXACT LSRL on your scatterplot, you can choose two x’s and plug in your equation to get two y’s and then plot the points OR you can use and then find one other point.
• Slope is a measure of rate of change. Y-intercept is what you would expect your y-value to be when x is zero.

1. In a Statistic course, a linear regression equation was computed to predict the final exam score from the score on the first test. The equation was y = 10 + .9x, where y is the final exam score and x is the score on the first test. Carla scored 95 on the first test. What is the predicted value of her score on the final exam? She actually scored a 98. What is her residual, and what does it mean?

1. A local community college announces the correlation between college entrance exam grades and scholastic achievement was found to be -1.08. On the basis of this, you would tell the college that
2. The entrance exam is a good predictor of success.
3. The exam is a poor predictor of success.
4. Students who do best on this exam will be poor students.
5. Students at this school are underachieving.
6. The college should hire a new statistician.

1. A researcher finds that the correlation between the personality traits “greed” and “superciliousness” is -.40. What percentage of the variation in greed can be explained by the relations with superciliousness?

1. Suppose we fit the least squares regression line to a set of data. What do we call any individual points with unusually large values of the residuals?

1. The table below shows the Men’s 800 Meter Run World Records (answer on a separate sheet):

1. Plot a scatterplot of the data.
2. Enter the data into your calculator and then perform least-squares regression. Write the LSRL equation and the correlation.

1. Describe the association in one sentence.

1. Draw the regression line on your graph. Identify the two points you used to create the line.

1. Construct a residual plot. Is this LSRL an appropriate model for the data?
2. Interpret the meaning of the slope for this data.

1. Predict the world record in the year 2005.

1. A university’s financial aid office wants to know how much it can expect students to earn from summer employment. This information will be used to set the level of financial aid. The population contains 3,478 students who have completed at least one year of study but have not yet graduated. A questionnaire will be sent to an SRS of 100 of these students, drawn from an alphabetized list.

(a)Describe how you will label the students in order to select the sample.

(b)Use Table B, beginning at line 105, to select the first five students in the sample.

1. Turkeys raised commercially for food are often fed the antibiotic salinomycin to prevent infections from spreading among the birds. However, salinomycin can damage the birds’ internal organs, especially the pancreas. A researcher believes that a combination of selenium and vitamin E in the birds’ diet may prevent injury. He wants to explore the effects of two different dosages of selenium (call them S1, S2) in combination with any of three different dosages of vitamin E (call them E1, E2, E3) added to the turkeys’ diets. There are 48 turkeys available for the study. At the end of the study, the birds will be killed  and the condition of their pancreas will be examined with a microscope.

a)What is the response variable?

b)Outline in diagram form an appropriate design for this experiment. In your diagram, indicate how many turkeys are assigned to each treatment group.