Question

Some of the stock in a winery has been found to be infected by Brettanomyces. You independently sample 80 barrels from the winery, and find that 28 of them are infected. Carry out a hypothesis test to evaluate the claim that half of the wine barrels are infected. What is closest to the p-value that you obtain

Answer 1

Explanation:

If half of the wine barrels are infected, it means that the proportion of infected wine is 0.5

We would set up the hypothesis test.

For the null hypothesis,

p = 0.5

For the alternative hypothesis,

p < 0.5

Considering the population proportion, probability of success, p = 0.5

q = probability of failure = 1 - p

q = 1 - 0.5 = 0.5

Considering the sample,

Sample proportion, P = x/n

Where

x = number of success = 28

n = number of samples = 80

P = 28/80 = 0.35

We would determine the test statistic which is the z score

z = (P - p)/√pq/n

z = (0.35 - 0.5)/√(0.5 × 0.5)/80 = - 2.68

From the normal distribution table, the area below the test z score in the left tail 0.0037

Therefore,

p value = 0.0037

Assuming a significance level of 0.05, therefore,

Since alpha, 0.05 > than the p value, 0.0037, then we would reject the null hypothesis.