1. A person's muscle mass is expected a decrease with age. To explore this relationship in women, 15 women from each 10-year age group, beginning with age 40 and ending with age 79, were randomly selected. The data is available on the E-learning under the file muscle mass.csv. # Read the data muscle = read.csv('muscle_mass.csv') Plot a scatterplot of age on the horizontal axis versus mass on the vertical axis. Do you think that a simple linear regression model is appropriate for this data? Briefly explain. Does the scatterplot in part (a) support the anticipation that muscle mass decreases with age? Briefly explain. Provide estimates of the slope and the intercept for the regression of mass on age. Draw the fitted regression line on the scatterplot in part (a). What is an estimate of the mean muscle mass for women aged 60 years? Compute the value of the residual for this observation. What is an estimate of 27 mn Recall that a residual is defined as e; = y; ;. Now compute >' e; for this dataset. Is it i=1 equal to zero