Apgar score is a number between 0 and 10 that gives a measure of the physical condition of a newborn infant. Researchers collected the Apgar scores of 2020 sets of identical twins to test if the first-born twin's score was, on average, different than the second-born twin's score.
What type of statical test used in this case?
A. A paired t-test for the mean difference
B. A two-sample z-test for the difference of proportions
C. A t-test for slope
D. A two-sample t-test for the difference of means
E. A z-test for a proportion
