Question

Among coffee drinkers, men drink a mean of 3.2 cups per day with a standard deviation of 0.8 cups. There is an outlier in this data making it positively skewed.

If a sample of 36 men is selected, what is the probability that the mean number of cups per day is less than 3?

Answer 1

Solution :

Given that,

mean = = 3.2

standard deviation = = 0.8

n = 36

= 0.8

=  / n = 0.8 / 36=0.13333

P( < 3) = P[( - ) / < (3-3.2) / 0.13333]

= P(z <-1.50 )

Using z table  

= 0.0668   

probability= 0.0668