The mean amount spent by a family of four on food per month is $507 with a standard deviation of $73. Assuming that the food costs are normally distributed.
a. what is the probability that a family spends less than $406 per month? Give your answer to 4 decimals.
b. what is the probability that a family spends at least $711 per month? Give your answer to 4 decimals.
Define random variable X : Food costs
X is normally distributed with Mean = and
Standard deviation =
a) Here we have to find P(X < 406)
where z is standard normal variable
= P(z < -1.38) (Round to 2 decimal)
= 0.0838 (From statistical table of z values)
Probability that a family spends less than $406 per month is 0.0838
b)
Here we have to find
(Round to 2 decimal)
= 1 - P(z < 2.79)
= 1 - 0.9974 (From statistical table of z values)
= 0.0026
Probability that a family spends at least $711 per month is 0.0026
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