Ascientist is studying the effects of cell phone use on headache rate. she identifies 30 people who use cell phones and 30 who do not. each of the 60 people is given a questionnaire designed to determine headache frequency. none of the 60 people who participated in the study knew they were part of a study. which statement is true? (5 points) question 5 options: 1) this is a randomized comparative experiment. 2) this is an observational study. 3) this is a double-blind study. 4) this is a matched-pairs design.

answer: a video game has three difficulty levels: easy, medium, and expert. the game's scoring works in such a way that a player has to score a fixed number of points to advance to the next level, and then the scoring starts over. the total score needed to clear all three difficulty levels is 7,500. two times the number of points needed to clear the easy level is 500 more than the number of points needed to clear the medium level. twice the number of points needed to clear the medium difficulty level is 1,500 more than the number of points needed to clear the expert level. if x, y, and z represent the easy, medium, and expert levels, respectively, and a is the coefficient matrix of the system of equations modeling this situation, identify the inverse matrix, a-1, and the solution matrix, x, of the system of equations.

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rauschg

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