##Question 2

Use the following commands to install the marketing dataset and load the datarium package into your session.

#install.packages("datarium") library(datarium) data("marketing", package = "datarium") str(marketing) ## 'data.frame': 200 obs. of 4 variables: ## $ youtube : num 276.1 53.4 20.6 181.8 217 ... ## $ facebook : num 45.4 47.2 55.1 49.6 13 ... ## $ newspaper: num 83 54.1 83.2 70.2 70.1 ... ## $ sales : num 26.5 12.5 11.2 22.2 15.5 ... 

1. Find the covariance between the Sales and the advertising budget of newspaper. Comment on the output, in terms of the strength and direction of the relationship.

#INSERT YOUR ANSWER HERE 

1. Plot the Sales as a function of the Youtube variable using a scatterplot, then graph the least-square line on the same plot. Hint: You may use the ggplot() function from ggplot2 package.

#INSERT YOUR ANSWER HERE 

1. Use the regression line to predict the Sales amount when newspaper budget is $136.80K. Comment on the difference between the output and the expected value.

#INSERT YOUR ANSWER HERE 

1. Use newspaper and facebook variables to build a linear regression model to predict sales. Display a summary of your model indicating Residuals, Coefficients, ..., etc. What conclusion can you draw from this summary?

#INSERT YOUR ANSWER HERE 

1. Use the regression line to predict the Sales amount when newspaper budget is $136.80K and facebook is $43.92K.

#INSERT YOUR ANSWER HERE 

1. What is the difference between the output in (e) and the output in (c)

#INSERT YOUR ANSWER HERE 

1. Display the correlation matrix of the variables: youtube, facebook, newspaper and sales. What conclusion can you draw?

#INSERT YOUR ANSWER HERE 

1. In your opinion, which statistical test should be used to discuss the relationship between youtube and sales? Hint: Review the differnce between Pearson and Spearman tests.

#INSERT YOUR ANSWER HERE