A test consists of 20 problems and students are told to answer any 15 of these questions. In how many different ways can they choose the 15 questions?

15,504

20,145

23,670

25,890

1. draw a histogram from all the data. starting at the bottom row, for each set of 10 flips, place an "x" in the column corresponding to the number of heads that set produced. your histogram should look similar to the example below: 2. calculate the mean and standard deviation. mean = standard deviation = 3. calculate the percent of the data that is within 1, 2, and 3 standard deviations of the mean. within 1 standard deviation = % within 2 standard deviations = % within 3 standard deviations = % 4. compare your results to a normal distribution. interpret any differences.