Find the lettered angle

Which measurement is the most precise? a) 29 cm b) 28.8 cm eliminate c) 28.76 cm d) 28.762 cm

Answer this question, only if you know the answer. 30 points and brainliest!

Researchers were interested in whether relaxation training decreases the number of headaches a person experiences. they randomly assigned 20 participants to a control group or a relaxation training group and noted the change in number of headaches each group reported from the week before training to the week after training. which statistical analysis should be performed to answer the researchers' question?