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Suppose that the store manager of a small rural pharmacy is doing a linear regression of daily sales of over-the-counter (OTC) decongestant nasal sprays on forecasted pigweed pollen count. He would like to determine if he can use a straight ine equation to predict OTC decongestant nasal spray sales from the allergy forecast for pigweed pollen. The store manager records the data for five random days. The pollen forecast is for pigweed only and is given in parts per square meter (ppm )2
Pollen forecast OTC decongestant sales (dollars)
14 $101
19 $89
13 $48
6 $21
9 $47
The store manager calculates the regression equation for the data as 5.514x-6.073.
Determine the standard error of the slope of the regression line, SEb, for the data. Give your answer precise to at least three decimal places SE=______.

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Answer:

3.83

Step-by-step explanation:

Mean of x = Σx / n

Mean of x = (14 + 19 + 13 + 6 + 9) / 5 = 12.2

Sum of square (SS) :

(14-12.2)^2 + (19-12.2)^2 + (13-12.2)^2 + (6-12.2)^2 + (9-12.2)^2 = 98.8

Mean of y = Σy / n

Mean of y = (101 + 89 + 48 + 21 + 47) / 5 = 61.2

Σ(y - ybar)² = (101-61.2)^2 + (89-61.2)^2 + (48-61.2)^2 + (21-61.2)^2 + (47-61.2)^2 = 4348.8

df = n - 2 = 5 - 2 = 3

Σ(y - ybar)² / df = 4348.8 / 3 = 1449.6

√(Σ(y - ybar)² / df) = √1449.6 = 38.074

Standard Error = √(Σ(y - ybar)² / df) / √SS

Standard Error = 38.074 / √98.8

Standard Error = 3.83

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