imagine that you developed a vaccine for the flu that infected our fictitious simploids. what is the minimum proportion of the population to vaccinate to establish herd immunity (pc) if this flu has an r0 of 4.0

Sole with work in 10 years, the average number of hours of tv watched per week by teenagers dropped from 23.9 to 21.4. find the percent of change.

The distribution of the amount of money spent by students for textbooks in a semester is approximately normal in shape with a mean of $235 and a standard deviation of $20. according to the standard deviation rule, how much did almost all (99.7%) of the students spend on textbooks in a semester?

Officer brimberry wrote 32 tickets for traffic violations last week, but only 4 tickets this week. what is the percent decrease? give your answer to the nearest tenth of a percent.