We wish to know whether supplementing the diet with extra quantities of vitamin A makes a difference in ability to see under conditions of dim illumination. We randomly assign 20 subjects to one of two groups, and feed one group a normal diet and the other a normal diet plus supplementary vitamin A. After 1 week under this regimen, each individual is tested for visual acuity in conditions of dim illumination. The following visual acuity scores are obtained (a) State formally the hypotheses necessary to conduct a non directional test of no difference between the two population means. (b) Complete the test at the .05 level of significance, and state your conclusions. (c) Does the result mean that H0 is true? Explain. (d) Compute the estimated effect size, g, and r.