Question

An experiment was conducted to compare the growth of Douglas fir seedlings under three different levels of vegetation control (0%, 50% and 100%). 16 seedlings were randomized to each level of control. The resulting sample means for stem volume were 58, 73, and 105 cubic centimetres (cm3), respectively with sp = 17 cm3. The researcher hypothesized that the average growth at 50% control would be less than the average age of the 0% and 100% levels.

a. What are the coefficients for testing this contrast?

b. Perform the test and report the test statistic, degrees of freedom, and P-value. Do the data provide enough evidence to support this hypothesis?

Answer 1