Suppose that a polling company surveyed 600 people about how much time they spend sleeping each night. The results of this survey were compiled and used to create this relative frequency histogram. 30- Relative frequency (%) 10 Nightly hours of sleep Assume that all percentages shown in the histogram are whole numbers. Each of the bars in this histogram includes only the left endpoint of the class except for the last bar, which also includes the right endpoint. What percentage of respondents said that they sleep less than six hours per night? 28 How many respondents said that they sleep between seven and nine hours per night? respondents