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# Homework 8 STAT 110 001

USC

GPA 3.6

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This 3 page Bundle was uploaded by Haley Johnson on Tuesday April 5, 2016. The Bundle belongs to STAT 110 001 at University of South Carolina taught by Wendy Cimino in Spring 2016. Since its upload, it has received 78 views. For similar materials see Introduction to Statistical Reasoning in Statistics at University of South Carolina.

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Date Created: 04/05/16

Homework 8 1. Use the graphs below to answer the following question. Which of these graphs has the strongest positive correlation? a.Graph 1 Positive correlation is when the plots are close to the slope line going up instead of spread out. 2. A study showed that students who study more hours tend to do better on statistics exams. In fact, number of hours studied explained 81% of the variation in exam scores among the students who participated in the study. What is the correlation between hours studied and exam score? a. R= 0.9 i. To find the correlation the percentage gives the given that r^2= 0.81. Taking the positive square root yields r = 0.9. We use the positive root because the first sentence of the problem indicates that the direction of the association between number of hours studied and test score is positive. 3. Thomas measured height in inches and weight in pounds and obtained a correlation coefficient of 0.87. He later decided to measure height in centimeters instead of inches. How will the value of the correlation coefficient change? a. It will not change; the correlation coefficient will still be 0.87. i. It will not change because both x and y values didn’t change 4. The Aimco Job Placement Agency gathers data from a survey about the number of years of college and their clients' starting salaries. The results were tabulated and a least-squares regression line was generated. The regression equation y = 8.2 + 11.44x represents the relationship between number of years of college experience (x) and starting salary (y) (in thousands). The r-squared value is 0.888. The r-squared value tells us that a. Approximately 89% of the variation is explained by the straight-line relationship between x and y. i. The r value represents the overall percentage of the line as it compares the x and y 5. The Aimco Job Placement Agency gathers data from a survey about the number of years of college and their clients' starting salaries. The results were tabulated and a least-squares regression line was generated. The regression equation y = 8.2 + 11.44x represents the relationship between number of years of college experience (x) and starting salary (y) (in thousands). The r-squared value is 0.888. What would be the starting salary if you had no college experience? a. 8.2 thousand dollars i. You use the formula y=a+bx ii. B=slope and a=intercept (Value of y when x=0) iii.What would y(Salary) be based on x(college experience)? iv. y=8.2 + 11.44(0) v. y=8.2 + 0 vi. y=8.2 6. The Aimco Job Placement Agency gathers data from a survey about the number of years of college and their clients' starting salaries. The results were tabulated and a least-squares regression line was generated. The regression equation y = 8.2 + 11.44x represents the relationship between number of years of college experience (x) and starting salary (y) (in thousands). The r-squared value is 0.888. The slope of the line suggests that a. For each year of experience the salary increases 11.44 thousand each year i. The slope means what it takes the move up 7. The Aimco Job Placement Agency gathers data from a survey about the number of years of college and their clients' starting salaries. The results were tabulated and a least-squares regression line was generated. The regression equation y = 8.2 + 11.44x represents the relationship between number of years of college experience (x) and starting salary (y) (in thousands). The r-squared value is 0.888. Use the regression equation to determine the starting salary of someone who has 6 years of college experience. a. 76.84 thousand dollars i. You use the formula y=a+bx ii. B=slope and a=intercept (Value of y when x=0) iii.What would y(Salary) be based on x(college experience)? iv. y=8.2 + 11.44(6) v. y= 8.2 + 68.64 vi. y=76.84 A sociologist wants to discover whether the sexual activity of females between 15 and 19 years of age and family structure are associated. She randomly selects 380 females between 15 and 19 years of age and asks each to disclose her family structure at age 14 and whether she has had sexual intercourse. The results are shown in the table below. Sex or no Both Single Stepparent Nonkind Total parents and reg parent parent (guardian) Sex 64 59 44 32 199 No Sex 86 41 36 18 181 Total 150 100 80 50 380 8. What is the probability that a randomly selected female between the ages of 15 and 19 has had sexual intercourse and is from a single parent family? a. 59/380 i. Number of females who had sex/total ii. You use the table total instead of the column or row total because there was no given in the question. 9. What is the probability that a randomly selected female between the ages of 15 and 19 has had sexual intercourse, given she is from a single parent family? a. 59/10 0 i. Total of girls who had sex from single fam/total of single fam column ii. You use the total of the column, because the given was the single fam. iii. If there is a given, the given total always goes as the denominator. 10. What is the expected count of females from a single parent family who have had sexual intercourse? a. 52.4 i. Expected count: row total X column total/table total ii. Sex row total X single fam column total/table total iii.(199 X 100) / 380 iv. 19,900/380 v. 52.37 = 52.4

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