In: Statistics and Probability
Question 2
In a study of the relationship between X = mean daily temperature for the month and Y = monthly charges on the electrical bill the following data was gathered:
Temperature (oF): Xi |
16 |
28 |
13 |
22 |
25 |
19 |
Number of Calls: Yi |
95 |
120 |
70 |
115 |
130 |
85 |
We are interested in fitting the following simple linear regression model: Y = Xβ + ε
a) Calculate X′X, (X′X)-1 and X′Y and then calculate the least squares estimates of β0 and β1.
b) Calculate the variance-covariance matrix of b, and use it to perform a t-test to test the null hypothesis that β1 = 0. Use α = 0.05.
Use the matrix approach to calculate the following:
c) Calculate a 95% confidence interval for the mean of Y when X = 20.
d) Calculate a 95% prediction interval for an individual new value of Y when X = 20.