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?

lo.lll

step-by-step explanation:

introduction, methodology, results, discussion

step-by-step explanation:

an observational study is one which consists of actual observation to record data and then analyse the data.

there are a number of factors that should be analyzed before starting an observational study.

the main four factors are:

i) introduction:   this should be analysed to check whether the purpose of the study is correctly established and the data recorded are appropriate for the study

methodology:   the method of collecting the data, such as whether randomly selected, and whether sample size matches with the population to be studied, whether questions asked are easy to answer by common men, etc.

results: then results such as summary of data with comments should be studied thoroughly

discussion:   the last is the discussion, this can be either by management people or persons who are all interested , etc.

i think the answer is b.

step-by-step explanation:

not 100% sure though.