Department of Economics

ECON 317 Introduction to Statistics for Economists

Prof. Safarzadeh

Assignment # 2 Student Name: ________________

Answer all the questions on the spaces provided. Underline your answers and show your calculations and work on the tables.

Item |Speed |Mileage | | |X - X |(X- X)2 |(Y-Y) |(Y-Y)2 |(X-X)(Y-Y) | | | |1 | 30 | 25 | | | | | | | | | | |2 | 50 | 20 | | | | | | | | | | |3 | 35 | 23 | | | | | | | | | | |4 | 45 | 21 | | | | | | | | | | |5 | 40 | 23 | | | | | | | | | | |6 | 25 | 32 | | | | | | | | | | |7 | 60 | 15 | | | | | | | | | | |8 | 65 | 14 | | | | | | | | | | |9 | 70 | 10 | | | | | | | | | | |10 | 35 | 22 | | | | | | | | | | |11 | 30 | 25 | | | | | | | | | | |12 | 25 | 30 | | | | | | | | | | |13 | 55 | 17 | | | | | | | | | | |14 | 40 | 23 | | | | | | | | | | |15 | 30 | 24 | | | | | | | | | | |16 | 25 | 30 | | | | | | | | | | |17 | 20 | 35 | | | | | | | | | | |18 | 40 | 21 | | | | | | | | | | |19 | 30 | 28 | | | | | | | | | | |20 | 40 | 22 | | | | | | | | | | | | | | | | | | | | | | | |

I. The relationship between the speed and the gas mileage for a mid size car has been studied using the information above.

1- Develop a scatter diagram of speed and mileage, with speed in the horizontal axis.

2- Is there any relation between speed and gas mileage?

3- Compute the covariance between the speed and the gas mileage. What does it mean?

4- Compute the correlation coefficient between the speed and the gas mileage. What does it mean?

5- Graph a histogram of speed. Comment on the distribution of the speed.

6- Graph a histogram of gas mileage. Comment on the distribution of the mileage.

II. Descriptive Statistics

1. For each variable (speed and mileage) in the table above, find mean, median, and mode.

Mean Speed = Median X = Mode X =

Mean Mileage = Median Y = Mode Y =

2. Which of the three measures (mean, median, mode) is a better measure of central