Midterm 1A practice

# A point that is an outlier in the y vertical

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29. A point that is an outlier in the Y (vertical) direction always has a large residual. a. TRUE b. FALSE 30. You can always interpret the Y intercept of a regression line. 6

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RECORD YOUR ANSWERS TO THE ABOVE QUESTIONS ON THE ANSWER SHEET ON THE LAST PAGE. WE WILL ONLY GRADE WHAT IS ON THE ANSWER SHEET. NO EXCEPTIONS! SHORT ANSWER PROBLEMS. WRITE YOUR FINAL ANSWER IN THE BLANK PROVIDED. SHOW WORK FOR CALCULATIONS TO GET CREDIT. 31. In the equation of the regression line, “a” stands for the place where the _________________ variable equals zero.” 32. Dr. X uses study time (# hours studied) to predict exam score (100 points possible). Her data has a strong linear relationship. The slope of her regression line is 20. The units of the slope in her case is ____________________. (No statistical terms or explanations please.) 33. The _________________ of an experiment are the combinations of values of the factor that are randomly assigned to the subjects. 34. Suppose a manufacturer has recorded its cost of electricity (in dollars) and the total number of hours of machine time for their factory during a certain number of weeks. They want to use the data to estimate electric bills based on machine time. Their data analysis is below. The average cost for electricity per week is known to be \$1041.9. What is the average amount of machine time? Include units. Show your work. ANS________________ Descriptive Statistics: Time, Cost Variable N StDev Variance Minimum Q1 Median Time 52 2.664 7.099 6.000 8.000 11.000 Cost 52 258.9 67043.1 464.3 879.2 1018.8 Variable Q3 Maximum Time 13.000 15.000 Cost 1243.2 1598.1 Regression Analysis Predictor Coef SE Coef T P Constant 263.4 103.8 2.54 0.014 Time 71.654 9.284 7.72 0.000 7
35. Bob is doing a survey of Columbus residents to find out their opinions on having a casino built downtown. He takes a random sample of names from the Columbus phone book. His sampling plan contains bias due to _______________________. (Must be a ONE WORD statistical answer.) Use this info for problems 36-37: Suppose managers know that the average number of contacts they make with their clients is 10 per year. They also know the average number of sales per client per year is 652 units. Now they want to predict the number of sales using the number of contacts. Their analysis is below (n = 50). Coefficients Standard Error t Stat P-value Constant XXXX 43.4074727 -15.0385889 5.9306E-21 Contacts 35.0008935 1.39830769 25.0308955 2.1802E-31 Correlation 0.92 36. Find the number that is missing in the output above (denoted by “XXX”.) Give it the proper label and include the units.

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