According to Chemical Engineering an important property of fiber is its water absorbency. The average percent absorbency of 25 randomly selected pieces of cotton fiber was found to be 20 with a standard deviation of 1.5. A random sample of 25 pieces of acetate yielded an average percent of 12 with a standard deviation of 1.25. Is there strong evidence that the population mean percent absorbency for cotton fiber is significantly higher than the mean for acetate? Assume that the percent absorbency is approximately normally distributed and ISyE 3770: Homework Nine that the population variances in percent absorbency for the two fibers are the same. Use a significance level of 0.05.
A. Calculate the test statistic
B. Should we reject the null hypothesis?