Scores from Exam 1:

41 59 10 71 0 45 57 49 78 64 62 12 89 71 52 68 84 65 90 69 31 55 63 20 64 52 80 51 45 95 32 97 76 54 41 82 60

What is the mean and standard deviation of the above sample?

If we assume performance is a bell-shape curve:

If A’s should have a z-score of at least 1.25 (top 10%), what score would be the cut-off for an A?

If B’s should have a z-score of at least .25 (top 30%), what score would be the cut-off for a B?

If C’s should have a z-score of at least -.25 (above bottom 30%), what would be the cut-off?

Location of the k percentile: L = k * n

(where if you’re looking for the top 10%, k = .1)

(note, we use this formula for the first and third quartile with k = .25 and .75)

Class Curve:

Top 10% (90th percentile) of class gets an A, what’s the position in the above the lowest A?

Top 30% (to 10%, the 70th percentile) gets a B, what’s the position in the above of the lowest B?

Middle 40% gets a C (30th percentile to 70th percentile), what’s the position in the above of the lowest C?

Year / Poverty% / Unemp% / Predicted Y () / Residual
1980 / 13 / 7.6
1985 / 14 / 7.4
1990 / 13.5 / 5.2
1992 / 14.8 / 7.8
1995 / 13.8 / 5.6
1998 / 12.7 / 4.5
2000 / 11.3 / 4
2002 / 12.1 / 5.8
2005 / 12.6 / 5
2007 / 12.5 / 4.6
2009 / 14.3 / 9.5

Regress the Poverty Rate (Y) on the Unemployment Rate (X)

For each Unemployment Rate, calculate the predicted Poverty Rate (the 4th column)

Then find the residual (error, 5th column)

What is the r and r2, interpret both of these

Interpret b1

Interpret the Y intercept

Find the X intercept and interpret that

Predictions:

If the unemployment rate was to fall by 3% points, predict what happens to the poverty rate

If the unemployment rate rose to 11%, predict the poverty rate

Control (important assumption):

What the unemployment rate need to be in order to get the poverty rate to 10%?

Car Weight
(pounds) / Mileage
(mpg) / Predicted Y () / Residual
3175 / 27
3450 / 29
3225 / 27
3985 / 24
2440 / 37
2500 / 34
2290 / 37

Regress the Mileage on the Car Weight

Calculate the Predicted Y and the Residual

What is the r and r2, interpret both of these

Interpret b1

Interpret the Y intercept

Find the X intercept and interpret that

Predictions:

If you add 500 pounds to a car, what happens to the mileage?

If a car weighs 2800 pounds, what is the predicted mileage?

Control (important assumption):

How heavy should a car be if you want the mileage to be 50 mpg?