Standard deviation is the square root of variance, but variance is given by mean, so divide by number of samples. That is : 38.5/10 = 3.58. But standard deviation equals the square root of variance, so SD = the square root of 3.85 which is 1.96.
The virginal(s): The virginal, also called virginals, usually has a rectangular case with the keyboard across the wide side. As with the spinet, the strings run side-to-side relative to the player. Again, it saves on wallspace, and again they rate their own FAQ. Virginals were fairly early, 15th and16th centuries.
Harpsichord designates the whole family of similar plucked keyboard instruments, including the smaller virginals, muselar, and spinet. The harpsichord was widely used in Renaissance and Baroque music. During the late 18th century, it gradually disappeared from the musical scene, with the rise of the piano.