Which of the following statements represents a difference between a sample survey and an observational study? a)presence of population. b)inclusion of numerical data. c)people are aware that they are participating. d)ability to collect information.

Many newspapers carry a certain puzzle in which the reader must unscramble letters to form words. how many ways can the letters of emdangl be arranged? identify the correct unscrambling, then determine the probability of getting that result by randomly selecting one arrangement of the given letters.