a) Z = (score-mean)/SD
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.
b) Z = (score-mean)/SEm
SEm = SD/√n
Use same table.
A 4 to 7 month old baby sleeps an average of 14 hours per day. At this age, babies sleep patterns follow normal distribution with the standard deviation of 1.6
a) is it unusual for a baby to sleep under 12 hours aday?
b) In a random sample of 10 babies of this age,find the probability that the mean number of hours of sleep is below 13 hours.
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