6.S.1 To study the conversion of nitrite to nitrate in the blood, researchers injected four rabbits with a solution of radioactively labeled nitrite molecules. Ten minutes after injection, they measured for each rabbit the percentage of the nitrite that had been converted to nitrate. The results were as follows:

51.1 55.4 48.0 49.5

(a) For these data, calculate the mean, the standard deviation, and the standard error of the mean.

(b) Construct a 95% confidence interval for the population mean percentage.

(c) Without doing any calculations, would a 99% confidence interval be wider, narrower, or the same width as the confidence interval you found in part (b)? Why?