# Tutor profile: Ardhendu B.

## Questions

### Subject: Statistics

"Confidence in the probability value assigned to this process describes how often we can use the process to derive a correct inference about population value that the interval actually contains the true value." What does "how often we can use the process" mean? Does it mean that there is a limited number of times that we can use a particular process? "The probability value behind confidence is the probability value of describing the behavior of the estimating process" What does "describing the behavior of the estimating process" mean?

...does that mean in layman terms that "we're 95% confident that the mean is within this given range of values"? No, it doesn't. The technical reason for why the above is untrue is because the population mean is a constant and not a random variable. The probability that a constant falls within a range is either 0 or 1. Frequentist analyses don't model our state of knowledge with a probability distribution. What does "describing the behavior of the estimating process" mean? Let's try to break the above down into layman's terms. The confidence level describes the uncertainty associated with a sampling method. Suppose we use the same sampling method to select different samples and compute a different interval estimate for each sample. Call my first sample S1. S1 will come with its own interval estimate. So will S2 etc... Some of our intervals would contain the true population parameter whilst some would not. If we have a 95% confidence interval, we can say that we would expect 95% of our interval estimates to include the true population parameter.

### Subject: Physics

How Earth would have been, if it didn’t turn?

If the earth didn't rotate, the day-night system would stretch over a year. The obvious impact would be on the climate of the planet. We would have strong, high-speed winds, circulating the globe, due to the stark difference in pressure on the side facing the sun and the dark side at any point of time. Also, the seasons wouldn't be the same, it would depend on which side is facing the sun and at what point in its orbit the earth was. But more interesting would be the evolution of life on the planet. The life on earth, the current earth, has evolved around the day-night cycle. Animals and plants have their entire life cycle planned around the rotation of the earth. Most life would be underground I guess. And if life managed to evolve into higher forms, they would always be migrating, to the twilight zone, a band between the day side and the night side.

### Subject: Aerospace Engineering

Is it possible to accelerate as well well as decelerate a fluid flow using the same device and configuration during different conditions?

Yes, it is possible. For the described purpose we need to use a converging nozzle. A nozzle in a sub-sonic flow will accelerate the flow but incase of a supersonic flow will decelerate the flow, hence acting as a diffuser.

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