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Describe the difference between random assignment and random selection in group designs.

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Random Selection:
Random selection occurs when a sample is randomly drawn from a population. Here's an example. Let's suppose a group of scientists were interested in finding out about the effects of a particular reading program on students attending school in particular region. If the research team had a list of all of the students attending school in that region and randomly selected a group of students from that list, we could say that that sample had been randomly selected. ...

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Describe the difference between random assignment and random selection in group designs.

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Random Sample

A recent article in Buisness Week listed the best small companies. We are interested in the current results of the companies sales and earnings. A random sample of 12 companies was selected and the sales and earnings, in millions of dollars, are reported below.

Company Sales Earnings
($ millions) ($ earnings)

Papa John's International 89.2 4.9

Applied Innovation 18.6 4.4

Integracare 18.2 1.3

Wall Data 71.7 8.0

Davidson Associates 58.6 6.6

Chico's Fas 46.8 4.1

Company Sales Earnings
($ millions) ($ millions)

Checkmate Electronics 17.5 2.6

Royal Grip 11.9 1.7

M-Wave 19.6 3.5

Serving-N-Slide 51.2 8.2

Daig 28.6 6.0

Cobra Golf 69.2 12.8

Let sales be the independent variable and earnings be the dependent variable.

A. Draw a scatter diagragm.

B. Compute the co-efficient of correlation.

C. Compute the co-efficient of determination.

D. Interpret your findings in part B and C.

E. Determine the regression equation.

F. for a small company with 50.0 million in sales, estimate the earnings.

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