5.19. ★★ A student measures a quantity y many times and calculates his mean as
$$\bar{y} = 23$$ and his standard deviation as $$\sigma_y = 1$$. What fraction of his readings would
you expect to find between
(a) 22 and 24?
(b) 22.5 and 23.5?
(c) 21 and 25?
(d) 21 and 23?
(e) 24 and 25?