Researchers measured the number of neurons in the CA1 region of the hippocampus in the brains of eight persons who had died of causes unrelated to brain function. They found that these data were negatively correlated with age. The sample value of r was - 0.63.7.
(a) Is this correlation coefficient significantly different from zero? Conduct a test using a = 0.10.
(b) Suppose in part (a) you found that the correlation does significantly differ from zero. Does this provide evidence that aging is a cause for CA1 neuron loss? If not, what could be said? Briefly explain.