Statistics and Probability
posted by Adam on .
A research manager at CocaCola claims that the true proportion, p, of cola drinkers that prefer
CocaCola over Pepsi is greater than 0.50. In a consumer taste test, 100 randomly selected people
were given blind samples of CocaCola and Pepsi. 58 of these subjects preferred CocaCola. Is there
sufficient evidence at the 5% level of significance to validate CocaCola’s claim? Conduct an
appropriate hypothesis test using (i) the pvalue method and (ii) the critical value method.

Null hypothesis:
Ho: p = .50 >meaning: population proportion is equal to .50
Alternative hypothesis:
Ha: p > .50 >meaning: population proportion is greater than .50
Using a formula for a binomial proportion onesample ztest with your data included, we have:
z = .58  .50 >test value (58/100 = .58) minus population value (.50)
divided by
√[(.50)(.50)/100]
Using a ztable, find the critical or cutoff value for a onetailed test (upper tail) at .05 level of significance. The test is onetailed because the alternative hypothesis is showing a specific direction (greater than).
The pvalue will be the actual level of the test statistic. You can use a ztable to determine that value.
I hope this will help get you started.