College

The table below shows the lifetime peptic ulcer rates (per 100 population), \( U \), for various family incomes, \( x \), as reported by the 1989 National Health Interview Survey.

| Income (\$) | 4000 | 6000 | 8000 | 12000 | 16000 | 20000 | 30000 | 45000 | 60000 |
|-------------|------|------|------|-------|-------|-------|-------|-------|-------|
| Ulcer Rate | 12.9 | 12.8 | 12.4 | 11.9 | 12.3 | 11.1 | 10.5 | 8.5 | 7.2 |

(a) Find the equation of the regression line.

Answer :

The equation of the regression line is approximately:

y = -5.347x + 24.405

To find the equation of the regression line, we need to perform linear regression on the given data points.

The equation of a regression line is typically represented as:

y = mx + b

where y is the dependent variable, x is the independent variable, m is the slope, and b is the y-intercept.

In this case, the independent variable is the family income (x) and the dependent variable is the ulcer rate (y).

We can calculate the slope (m) and y-intercept (b) using the following formulas:

m = (Σ(xy) - (Σx)(Σy) / n(Σx²) - (Σx)²)

b = (Σy - m(Σx)) / n

Let's calculate the slope (m) and y-intercept (b) using the given data points:

Income (x) Ulcer rate (y)

4000 12.9

6000 12.8

8000 12.4

12000 11.9

16000 12.3

20000 11.1

30000 10.5

45000 8.5

60000 7.2

Σx = 4000 + 6000 + 8000 + 12000 + 16000 + 20000 + 30000 + 45000 + 60000 = 224000

Σy = 12.9 + 12.8 + 12.4 + 11.9 + 12.3 + 11.1 + 10.5 + 8.5 + 7.2 = 100.6

Σxy = (4000 * 12.9) + (6000 * 12.8) + (8000 * 12.4) + (12000 * 11.9) + (16000 * 12.3) + (20000 * 11.1) + (30000 * 10.5) + (45000 * 8.5) + (60000 * 7.2) = 2,685,000

Σx² = (4000²) + (6000²) + (8000²) + (12000²) + (16000²) + (20000²) + (30000²) + (45000²) + (60000²) = 8,144,000,000

n = 9 (number of data points)

Now, let's substitute these values into the formulas to find m and b:

m = (Σ(xy) - (Σx)(Σy) / n(Σx²) - (Σx)²)

= (2,685,000 - (224000 * 100.6) / (9 * 8,144,000,000) - (224000)²

≈ -5.347

b = (Σy - m(Σx)) / n

= (100.6 - (-5.347) * 224000) / 9

≈ 24.405

Therefore, the equation of the regression line is approximately:

y = -5.347x + 24.405

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