what is the test statistic

in 1 point Charles Darwin (1809 - 1882), the author of The Origin of Species (1859) investigated the effect of cross-fertilization on the size of plants. In this experiment, pairs of plants, one cross- and one self-fertilized, were planted and grown in the same plot. The following table gives the difference in height (eighths inches) for 15 pairs of plants (cross-fertilized minus self-fertilized Zea mays) raised by Charles Darwin. Use this data to evaluate the null hypothesis that the two methods are not different. Difference : 49, -67, 8, 16, 6, 23, 28, 41, 14, 29, 56, 24, 75, 60, -48 What is the test statistic