Stat Practice Exam 1 - yellow PDF

Preview

Summary

Study guide containing materials in detail from the course throughout the semester....

Description

Stat Practice Exam 1- Yellow 1.Fill in the Blanks: a. Choose from the following options: histogram, bar chart i. We can visually summarize the distribution of a categorical variable with a ____________ and that of a quantitative variable with a ____________. b. If the data does not follow the normal curve the _____________ represents the center of data. c. Choose one of the following options: influential, high leverage. i. _____________ points will always change our regression equation and conclusions substantially while ____________ points may not. d. Correlation coefficient measures the strength of the ___________ association between two variables. e. Under the normal curve, the area to the right of z = 0 is ___________. 2. True or False: a. Given r75 we expect the standard deviation of the residuals to be smaller than the standard deviation of the response. _____ b. A correlation coefficient r can be zero even though a strong relationship exists between the variables. ______ c. The correlation coefficient r can be zero even though a strong relationship exists between variables. d. Correlation coefficients range between 0 and 1. _______ e. For a histogram with a long right tail, more than half of the area is to the left of the average. ________ f. Both the standard deviation and the IQR provide a measure of spread. _____ g. The color of different cars in Bing parking garage is recorded as 1 if the color is green and 0 if it is not The quantitative measurement. _______ 3. Multiple Choice a. A correlation coefficient r = 1 implies i. The points all fall on a line, which slopes down, ii. The pints all fall on a line, which slopes up. iii. The points are tight clustered and overall slopes upwards. iv. The points are tight clustered and overall slopes downwards. b. The educational testing service computed the average verbal SAT score for each state, as well as the average Math SAT score for each state including D.C. The correlation between these 51 pairs if averages was 0.97. Then, the correlation between the Math SAT and the Verbal SAT computed from the data on all the individuals who took the tests i. Should be about .97 ii. Should be larger than .97 iii. Should be less than .97 c. Say a data point is converted to 1.5 standard units. Them, this implies that i. The data point is 1.5 SD above the mean ii. The data point is 1.5 raw data unites away from the average. iii. The data point is 1.5 SD away from the average. iv. None of the above d. The Correlation Coefficient i. Is not affected by outliers

ii.

Has the lowest possible value (including sign)for the wicked association and the highest possible value for the strongest association. iii. Satisfies none of the above. 4.Students were asked to describe their policies as “Liberal”, “Moderate”, “Conservative”. What is the marginal distribution of political views?

5. Some IQ tests are standardized to a Normal model, with a mean of 100 and a SD 16. About what percent of the people should have IQ scores between 68 and 84?

6. A cereal manufacturer has a machine that fills the boxes. Assume that the Normal model applies and a box weighing less than 16 oz. is considered underweight. The company's president sets the goal of the machine to average 16.2 oz and have only 4% underweight boxes. What SD must the machine achieve?

7.Marine biologists warn that the growing number of power boats registered in Florida

threatened existence of Manatees. Say the linear model is judged to be appropriate for the data on manatees killed and powerboat registration and an r^2 of 90.5% is obtained.

a. Identify the explanatory variable b. Find the correlation between Boat Registrations and Manatee Deaths. c. Describe the association (form, direction, strength) in the scatter plot. How will you interpret in context of the deaths and registrations?

D. Interpret r^2 E. Does the analysis prove that powerboats are killing manatees? Why or why not?

8. Here are residual plots for three linear regression models. Indicate which condition appears to be violated in each case.

9. A company that sells Dornish wine to stores in four makrts wants to examine the prices that taverns charge fo a glass of what they claim to be wine. Here are box plots comparing data from a sample of stores in each market.

a. Which market appears to be both higher on average, and more variable than every other market? b. WHich market has the most consistent pries?

10. The histogram shows the lengths of hospital stays in days for all the female patients

admitted to the hospitals in NY during one year with the primary diagnosis of heart attack.

a. Would you expect the mean or median to be higher and why? B. Describe the distribution in terms of the number of models and symmetry/skewness.

11. A manager of a bookstore wants to predict sales (y) from number of sales people working (x) and have the following data x bar = 10.4, y bar = 17.6, SD(x)=5.64, SD(y)=5.34, r=.965 a. Find the intercept the slope of b1

B. Find the intercept the intercept...