The manager of a store wants to have a sales promotion where she gives prizes to the first several people through the door. She
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The sample size should be 250.
Our margin of error is 4%, or 0.04. We use the formula
To find the z-score:
Convert 98% to a decimal: 0.98
Subtract from 1: 1-0.98 = 0.02
Divide both sides by 2: 0.02/2 = 0.01
Subtract from 1: 1-0.01 = 0.99
Using a z-table (http://www.z-table.com) we see that this value has a z-score of approximately 2.33. Using this, our margin of error and our proportion, we have:
Divide both sides by 2.33:
Square both sides:
Multiply both sides by n:
Divide both sides to isolate n:
Our margin of error is 4%, or 0.04. We use the formula
To find the z-score:
Convert 98% to a decimal: 0.98
Subtract from 1: 1-0.98 = 0.02
Divide both sides by 2: 0.02/2 = 0.01
Subtract from 1: 1-0.01 = 0.99
Using a z-table (http://www.z-table.com) we see that this value has a z-score of approximately 2.33. Using this, our margin of error and our proportion, we have:
Divide both sides by 2.33:
Square both sides:
Multiply both sides by n:
Divide both sides to isolate n: