Question

a. Using the following R codes to fit the linear regression model for VitC on HeadWt, and obtain its summary. Paste the R output in your homework. cabbages_data <- read.csv("http://users.stat.umn.edu/~wuxxx725/data/cabbages_data.csv") cabbages_reg <- lm(VitC ~ HeadWt, data = cabbages_data) summary(cabbages_reg) b. State and interpret the value of r 2 from the model summary output in part a). c. Calculate the correlation r between HeadWt and VitC, and state the strength and the direction of the correlation. d. State the estimated regression equation in the form VitC ˆ = a + b(HeadWt). e. Interpret the slope b in the estimated regression equation in part d). f. Cabbage head #20 had a weight of 2.0 kg. Predict its vitamin C content using the estimated regression equation in part d).

g. The actual vitamin C content for cabbage head #20 was 60 mg/100 g. Find its residual based on your answer in parts f). h. How would the correlation r between HeadWt and VitC change, if HeadWt were measured in pounds instead of kilograms? Please explain. (1 kg = 2.205 lbs) i. Check the linearity, normal error, and constant variance assumptions using the following plots. j. Conduct a five-step hypothesis test on whether the true slope β is different from 0 at the significance level 0.05.

Answer 1

Note: The first 5 questions have been solved. Post the remaining as a new post, PLEASE