Probability

[Vemuri]

A researcher is experimenting with several regression equations. Unknown to him, all of his formulations are in fact worthless, but nonetheless there is a 5 per cent chance that each regression will-by the luck of the draw-appear to come up with `significant’ results. Call such an event a `success’. If the researcher tries 10 equations, what is the probability that he has exactly one success? What is the probability of at least one success?

Source: a gmat preparing forum.

[scoobydooby]

chance of a success: 5%=>chance of a failure: 95%

1) exactly 1 success out of 10 equations
=10C1*0.05*(0.95)^9
=10*5/100*(0.95)^9
=1/2*(0.95)^9


2) atleast one success
=1-probability of no success
=1-(0.95)^10