For each of the following research studies, identify whether independent samples (e.g., two-sample t test, Wilcoxon-Mann-Whitney) or paired samples (e.g., paired t test, sign test) would most likely be appropriate and explain why.
(a) To investigate whether or not there are differences in turbidity (i.e.. suspended sediment) at the surface of a stream versus near the bottom, 15 stream locations were sampled, and turbidity measurements were made at the surface and depth of 0.5 meters.
(b) To investigate if a marine protection policy off the coast of California improves the health of rockfish. researchers measured catch per unit effort (a surrogate measure for fish abundance) at eight rockfish habitat locations inside a marine protected area and eight additional nearby habitat locations outside the protected area.
(c) To compare the therapeutic value of different milk-based supplements in malnourished children, researchers randomly assigned one of two common supplements (10% milkor25% milk) to approximately 1,900 malnourished children in rural Malawi and measured their weights at the start of the study, and again after 8 weeks of therapy.