In her geology class, Nora learned that quartz is found naturally in a variety of colors. Nora's teacher has a giant box of colorful quartz pieces that he and his students have collected over the years. Nora picks a piece of quartz out of the box, records the color, and places it back in the box. She does this 18 times and gets 3 purple, 2 yellow, 5 white, and 8 pink quartz pieces.