A certain type of yarn is manufactured under specifications that the mean tensile strength must be 20 pounds. A random sample of 16 specimens yields a mean tensile strength of 18 pounds and a standard deviation of 3.2 pounds. Can we conclude from these data that the mean tensile strength for the population is less than 20 pounds? Assume that the tensile strengths are approximately normally distributed. Let alpha = 0.05.
Draw the null distribution, including the critical value and the test statistic
Estimate the p-value
What is the conclusion?