Question

The mean amount spent by a family of four on food per month is $700 with a standard deviation of $85. Assuming that the food expenditures are normally distributed, what is the proportion of families of four that spend more than $900 per month?

Answer 1

0.93% of the persons spend above 900 dollars on food per month

Step-by-step explanation:

Pz = (X - mean) / standard deviation

Pz = (900-700)/85 = 2,3529

Now we look for the value of a Pz of 2.35 in a normal distribution table to know the accumulated persons which are below 900 per month

PZ 2.3529 = 0.99068721

there is a 0.99068721 of the population which spend less than 900 per month on food

We now do 1 - 0.99068721 = 0,00931279‬ = 0.93% this is the percentage of person who spend above 900 dollar per month on food