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Sun 9 Apr, 2017 05:57 pm
The average tree planter earns $95/day with a standard deviation of $20. The distribution is normal.
a) Most students won't accept a job that pays less than $70/day. What percentage of the planters make less than this minimum?
b) We decide to increase the average pay by paying a fixed daily allowance in addition to the money the planters earn planting. How large of an allowance should we pay so that 95% of the planters make $70 or more per day?
c) Another company has decided to pay more for each tree planted. They expect a new mean of $105 and a standard deviation of $25. The distribution is normal. A random sample of 20 planters showed an average wage of $110. If the expected mean and standard deviation are correct, what percentage of sample means of size 20 would be less than $110?
@plebster447,
Calculate
z = (X - μ) / σ
where z is the z-score, X is the value of the element, μ is the population mean, and σ is the standard deviation.
Then look up a z score table to obtain the normally distributed probability.
http://www.statisticshowto.com/probability-and-statistics/z-score/
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