Question 235411
A telephone survey gives 670 consumers two choices: Do they prefer Coke or Pepsi?
Exactly 158 of those surveyed state that they prefer Coke. 
Assuming that alpha = 0.10, test the hypothesis that the proportion of the population that prefers Coke is 50%.
· State the null and alternate hypotheses
Ho: p = 0.5
Ha: p is not 0.5
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· Calculate the sample proportion
p-hat = 158/670 = 0.2358
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· Calculate the value of the test statistic.
z(0.2358) = (0.2358-0.5000)/sqrt[.5*.5/(670)] = -13.6773 
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· Determine the critical value(s).
invNorm(0.05) = +/-1.645
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Decision: Should Ho be rejected.
Yes because the test statistic is in the rejection interval
to the left of -1.645.
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Cheers,
Stan H.