Question

The average middle-distance runner at a local high school runs the mile in 4.5 minutes, with a standard deviation of 0.3 minute. Find the percentage of a runners that will run the mile in less than 4 minutes?
A. 45.22%

B. 15.87%

C. 7.15%

D. 4.75%

Answer 1

Convert 4 minutes to a z-score. Z-score is simply how many standard deviations from the mean a number is.
(x-mean)/(SD) = z-score

Once you've converted it to a z-score, look up that score on a z-table to find out what percentage of the data will be above or below it.

Answer 2

huuh ?

Answer 3

You've got a specific time you're interested in, right? How far is that time from the mean?

Answer 4

hmm ive never learned this so idk.____.

Answer 5

Honestly. I'm walking you through this. The only reason not to be able to answer the question I asked is because you're not trying.

Answer 6

but i dont get it i dont know what a zscore is i dont know what xmean is an deff dont know what SD means .

Answer 7

Mean is the same as average.
SD (standard deviation) describes how close or far most of the data is from the mean.

Answer 8

so add them together an that wouldbe our average . an i now its not b .