Researchers are interested in the effect of a certain nutrient on the growth rate of plant seedlings. Using a hydroponics grow procedure that utilized water containing the nutrient, they planted six tomato plants and recorded the heights of each plant 14 days after germination. Those heights, measured in millimeters, were as follows: 54.9, 59.7, 61.3, 63.4, 64.5, 71.5. The confidence interval turned out to be (56.7, 68.4). name two things you could do to get a narrower interval than the one already created. a) decrease the confidence level or decrease sample size b) decrease the confidence level or increase sample size c) increase the confidence level or decrease sample size d) increase the confidence level or increase sample size