Ahigh school principal wants to test the overall mood in his school. he stops the first fifteen students who come into the office one morning and asks them to rate their high school experience on a scale of 1 (worst) to 10 (best). the average response is 3.2, and the principal concludes that his school's mood is poor.
the principal's conclusion
a) is based on too small a sample.
b) is valid, since the students were chosen randomly.
c) is unfair, since he is the one running the school.
d) is invalid, since the students were chosen by convenience.

Titus works at a hotel. part of his job is to keep the complimentary pitcher of water at least half full and always with ice. when he starts his shift, the water level shows 4 gallons, or 128 cups of water. as the shift progresses, he records the level of the water every 10 minutes. after 2 hours, he uses a regression calculator to compute an equation for the decrease in water. his equation is w –0.414t + 129.549, where t is the number of minutes and w is the level of water. according to the equation, after about how many minutes would the water level be less than or equal to 64 cups?