A company that manufactures chocolate bars is particularly concerned that the mean weight of
a chocolate bar not be greater than 6.03 ounces. Past experience allows you to assume that the
standard deviation is 0.02 ounces. A sample of 50 chocolate bars is selected, and the sample
mean is 6.034 ounces. Using the + = 0.01 level of significance, is there evidence that the population
mean weight of the chocolate bars is greater than 6.03 ounces?
SOLUTION Using the critical value approach,
Step 1 H0: , 6.03
H1: > 6.03
Step 2 You have selected a sample size of n = 50. You decide to use + = 0.01.
Step 3 Because * is known, you use the normal distribution and the Z test statistic.
Step 4 The rejection region is entirely contained in the upper tail of the sampling distribution
of the mean because you want to reject H0 only when the sample mean is significantly
greater than 6.03 ounces. Because the entire rejection region is in the upper tail of the
standardized normal distribution and contains an area of 0.01, the critical value of the
Z test statistic is 2.33.