Standard Normal Probability ANSWER CHECK

Question

A group of retailers models that the amount of dollars X that an individual will spend in christmas
shopping has a normal distribution with mean μ = $1100 and standard deviation σ = $330. What
proportion (probability) of shoppers will spend more than $500?

 

P(500 < X) =

 

I plugged in 500 for the lower and 5 for upper, along with the mean and standard deviation.

When I used my calculator I got -0.0340650325 and I'm not sure if it is possible to get a negative so I wanted to check.

Answer 1

You may need to draw a diagram.  The area you need to calculate is from 1.82 standard deviates left of the mean to +infinity which is .5 + the area from the mean to 1.82 s.d. out, which according to my table is .4656.  That is almost 97% of people spend more than $500.