STAT 216 Midterm: STAT 216 Montana State Exam1F04

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turquoisegnu128

15 Feb 2019

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In each of the following multiple choice questions choose the single best answer. In french, she scored 82 and in math, 84. The overall results on the french exam had a mean of 72 and a standard deviation of 8, while the mean math score was 70 with a standard deviation of 12. 1: three statistics classes, each with 24 students, all took the same test. Histograms of the scores for each class are shown below. Class 3: class 1, class 2, class 3, cannot tell, a small college has 600 freshmen, 400 sophomores, 300 juniors, and 250 seniors. A simple random sample of 50 undergraduates is taken from each of these categories, giving a combined sample of 200 students. This is an example of: a simple random sample, a matched sample, a strati ed random sample, a multistage sample.

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In a large class, there were 274 students who wrote both the midterm and the final exam. The standard deviation of the midterm grades was 13, and that of the final exam was 16. The correlation between the grades on the midterm and the final was 0.6.

Based on the least squares regression line fitted to the data of the 274 students, if a student scored 19 points below the mean on the midterm, then how many points below the mean on the final would you predict her final exam grade to be?

The predicted final exam grade is below the mean on the final. (Round your answer to one decimal place, but do not round in intermediate steps.)

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Opeele Kyinkafa sells different used 2005 GM cars in excellent condition. The value or the retail price (Price) of a car is dependent on a variety of characteristics such as number of miles the car has been driven (Mileage), manufacturer of the car (Make) such as Buick, Cadillac, Chevrolet, Pontiac, SAAB, and Saturn. The car price is also influenced by the body type (Type) such as sedan, convertible, coupe, hatchback and wagon. It is also affected by number of cylinders (Cylinders) in the engine, the engine size (Liter), cruise control which is an indicator variable representing whether the car has cruise control (yes) or no otherwise and Sound indicator representing whether the car has upgraded speakers (yes) or no otherwise. All cars in this data set were less than one year old when priced and considered to be in excellent condition. Determine which major variables are dummies and are dynamic? Identify 3 potential unobserved heterogenous factors in this dataset. Display the full descriptive statistics of the data in R. Why do you think some variables are starred (*)? What is the median for “price”, standard deviation for “mileage”, skewness for “cylinder” and mean for “sound”? Test if “price” is normally distributed using histogram, kernel density plot and the shapiro wilk test. Create a red scatterplot matrix of price, mileage, cylinder, liter, make. From your graph, is the correlation between price & mileage positive or negative? What’s the pearson correlation coefficient between price & mileage and between “cylinder” & “liter” correct to 2 d.p Create a correlation matrix of the dataset by finding the apt R command for converting all string/dummy variables From the matrix, identify 2 potentially good predictors? Identify 3 pairs of variables that are mostly multicollinear. Which 2 pairs of variables are least correlated? Identify 3 pairs of variables most highly correlated with Cylinder Generate a simple regression plot of price on mileage with a re fitted line. Run the whole multiple regression model (label the equation as "regprice") & use it to answer the other questions. Specify the regression model for the whole data keeping the exact names of the variables. Write the estimated regression equation. In one sentence, which variables are significant and which are not? Justify Is the regression model justifiable? Explain Interpret the coefficient of Mileage, MakeCadillac, TypeSedan, Cylinder, & Cruiseyes. Compare the price of a car with 130,000 mileage, 6 cylinders, 3.8 liters, with cruise and sound, was manufactured by Pontiac with a convertible body type with that of the price of a car with four cylinders, 120,000 mileage, 3.8 liters, without cruise nor sound, was manufactured by Cadillac with a hatchback body type. Which factor(s) appears to be causing a comparative difference (if any)? Using only the VIF, which one of the pairs of variables selected to be multicollinear may be deleted? Justify?

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STAT 216 Midterm: STAT 216 Montana State Exam1F04

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