The authors of the article ‘a probabilistic insulation life model for combined thermal-electrical stresses" (ieee trans. onelect. insulation, 1985: 519—522) state that "the weibull distribution is widely used in statistical problems relating to agingof solid insulating materials subjected to aging and stress." they propose the use of the distribution as a model for time (inhours) to failure of solid insulating specimens subjected to ac voltage. the values of the parameters depend on thevoltage and temperature; suppose a and b = 200(values suggested by data in the article).a. what is the probability that a specimen's lifetime is at most 250? less than 250? more than 300? b. what is the probability that a specimen's lifetime is between 100 and 250? c. what value is such that exactly 50% of all specimens have lifetimes exceeding that value?

a) one student is chosen from classroom a, then a student is chosen from classroom b.  

step-by-step explanation:

independent events are ones in which the probability of one event does not affect the probability of the second event.

one student is chosen from classroom a; this does not affect the chances of choosing a student from classroom b.   this makes these independent events.

when one card is chosen from a standard deck and then set aside before a second card is chosen, the probability of the second card being chosen changes.   this makes them dependent events.

when one student is chosen from classroom a and then a second student is chosen from classroom a, the probability of choosing the second student changes.   this makes them dependent events.

when a letter is chosen from the alphabet and then a second letter is chosen, the probability of choosing the second letter changes.   this makes them dependent events.