Question

Canadian couples spend an average of $25038 to cover the cost of their weddings. Determine the cutoff of the top 10% of wedding costs if the standard deviation is $2094 and the data is normally distributed (USING EXCEL SOFTWARE)

Answer 1

the PDF of normal distribution is = 1/σ * √2π * e ^ -(x-u)^2/ 2σ^2
standard normal distribution is a normal distribution with a,
mean of 0,
standard deviation of 1
equation of the normal curve is ( Z )= x - u / sd ~ N(0,1)
mean ( u ) = 25038
standard Deviation ( sd )= 2094

the cutoff of the top 10% of wedding costs
P ( Z > x ) = 0.1
Value of z to the cumulative probability of 0.1 from normal table is 1.2816
P( x-u / (s.d) > x - 25038/2094) = 0.1
That is, ( x - 25038/2094) = 1.2816
--> x = 1.2816 * 2094+25038 = 27721.569