Z = (score-mean)/SD
1. Z = (470-400)/45 = ?
2. Use same equation for both values.
3. Find Z score in table and work backwards.
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability related to the Z score(s).
the life time of a certain kind of mean life of 400 hours and standard deviation of 45 hours. assuming the distribution of life time to be normal, find : 1. the percentage of batteries with a life time of atleast 470 hours 2. the proportion of batteries with a lifetime between 385 and 415 hours 3. the minimum life of the best 5% of the batteries
1 answer
1 answer