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Help with statistics question PLEASE?
An airline conducts the following research. Average evacuation time in the past has been 100 seconds with a standard deviation of 15 seconds.
If the airline conducts a sample of 30 tests, what is the probability that the average evacuation time will be 97 seconds or less?
1 Answer
- 1 decade agoFavorite Answer
the std dev of sample means (ss) is std dev of pop/sqrt(sample size)
ss= 15/sqrt(30)=15/5.48=2.73
z=(xbar-mean)/sd
change 97 to a z-score
z=(97-100)/2.73
z=-3/2.73=-1.10
z=-1.10
central area for z=-1.10 is .3643
area in question is to LEFT of that area (tail end)
subtract from .5
.5000-.3643=.1357 (answer)
Source(s): http://www.math911.com/